Abstract
Background
Physical activity after breast cancer diagnosis is associated with improved survival. This study examines levels of and changes in physical activity following breast cancer diagnosis, overall and by race.
Methods
The Carolina Breast Cancer Study, Phase III, assessed pre- and post-diagnosis physical activity levels in a cohort of 1,735 women, aged 20–74, diagnosed with invasive breast cancer between 2008 and 2011 in 44 counties of North Carolina. Logistic regression and analysis of variance were used to examine whether demographic, behavioral and clinical characteristics were associated with activity levels.
Results
Only 35% of breast cancer survivors met current physical activity guidelines post-diagnosis. A decrease in activity following diagnosis was reported by 59% of patients, with the average study participant reducing their activity by 15 metabolic equivalent (MET) hours (95% CI: 12, 19). Following adjustment for potential confounders, when compared to white women, African-American women were less likely to meet national physical activity guidelines post-diagnosis (odds ratio: 1.38, 95% CI: 1.01, 1.88) and reported less weekly post-diagnosis physical activity (12 vs. 14 MET-hours; p=0.13). In adjusted, stratified analyses, receipt of treatment was significantly associated with post-diagnosis activity in African-American women (p<0.01).
Conclusion
Despite compelling evidence demonstrating the benefits of physical activity post-breast cancer, it is clear that more work needs to be done to promote physical activity in breast cancer patients, especially among African-American women.
Introduction
Participation in regular physical activity following breast cancer is associated with reduced morbidity and higher quality of life.1–4 It has also been associated with improved overall and breast-cancer specific survival.5–8 Findings from a meta-analysis show that the mortality rate is reduced by 34% in those with higher levels of reported activity when compared to those with the least amount of physical activity after breast cancer diagnosis.9 Declines in physical activity following breast cancer diagnosis have also been associated with reduced overall survival.10
These compelling findings regarding benefits derived from participation in physical activity following breast cancer diagnosis have been promoted in healthcare and other settings and have led to calls for physical activity to be incorporated into models of breast cancer care.11–13 However, before a change in clinical practice can be supported, it is first important to understand whether there is capacity for change in the physical activity levels of women with breast cancer.
The US Department of Health and Human Services, as well as the American Cancer Society, recommends that adults engage in at least 150 minutes of moderate-intensity physical activity or 75 minutes of vigorous-intensity physical activity (or an equivalent combination thereof) each week for general health benefits and for chronic disease prevention and management.14–16 Estimates of the percentage of breast cancer survivors who meet current physical activity guidelines prior to their diagnosis range widely, from 34% 17 to 70%,18 however, many studies have found that survivors tend to decrease their activity level post-diagnosis, with percentage reductions ranging from 3% to 50%.18–21 Preliminary studies have suggested that racial disparities may exist in post-diagnosis physical activity, with African-American women less likely to meet physical activity recommendations after a diagnosis1, 17, 22 and more likely to report higher declines in post-diagnosis physical activity compared with white women.18 However, many of these studies did not report on change in physical activity by race, included a small sample of African-Americans in their study populations, or were not population-based.1, 17, 22 Because of the higher rates of morbidity and mortality experienced by African-American women compared with white women,23, 24 further study of this relationship is warranted.
The purpose of this study was to describe post-diagnosis physical activity and changes between pre- and post-breast cancer diagnosis physical activity levels, overall and by race in a population-based study of breast cancer patients with a large group of African-American women.
Methods
Study Population
Phase III of the Carolina Breast Cancer Study (CBCS) is a prospective, population-based survivorship cohort study based in 44 counties in eastern and central North Carolina.25 Eligibility for study participation was limited to those who were female, English-speaking, newly diagnosed with invasive breast cancer, and between 20 to 74 years of age. Younger women and African-American women were oversampled to make up 50% of the total population to ensure sufficient power for subgroup analyses. Cases were identified and randomly recruited from the North Carolina Cancer Registry between 2008 and 2011.
Data Collection
The CBCS Phase III involves data collection by trained personnel at regular intervals for up to 5 years post-diagnosis. The work presented within this paper reflects data collected at the baseline in-person interview by study nurses, conducted at approximately 6 months-post-diagnosis (mean± standard deviation = 5.7± 2.9 months).
Total Physical Activity
At the baseline interview, women were asked to self-report the usual amount of vigorous- and moderate-intensity physical activity they completed in the three months prior to their breast cancer diagnosis and in the seven days prior to the baseline interview. The questions were patterned on those used in the 2001 Behavioral Risk Factor Surveillance System survey26 and provided examples of moderate-intensity (e.g., brisk walking, vacuuming, and gardening) and vigorous-intensity physical activity (e.g., running and heavy yard work).26
Total weekly minutes of physical activity post-diagnosis was evaluated as a continuous (total minutes/week) and categorical variable (sufficiently active, insufficiently active or sedentary). Total minutes of physical activity per week was calculated as 2*vigorous activity + moderate activity.26 Categories were based on meeting the US Department of Health and Human Services recommendations. Specifically, those reporting ≥ 150 minutes total physical activity per week were sufficiently active, those reporting >0 minutes but < 150 minutes per week were insufficiently active, and those reporting no activity were classified as sedentary. Change in physical activity levels between pre- and post-diagnosis was also assessed as a continuous (post-diagnosis levels minus pre-diagnosis levels) and categorical variable (increased: increased activity by ≥ 30 minutes compared to pre-diagnosis amount; decreased: decreased activity by ≥ 30 minutes; no change: reported activity levels at post-diagnosis were within 30 minutes of pre-diagnosis levels). Physical activity levels were also used to calculate total weekly metabolic equivalent task (MET)-hours per week. MET values of 4.0 and 8.0 were assigned to moderate- and vigorous-intensity activity, respectively (based on the International Physical Activity Questionnaire Guidelines),27 were multiplied by reported number of hours per week for each activity type and then summed across these amounts. To determine if high levels of reported physical activity affected data interpretation, a sensitivity analysis was conducted by truncating reported weekly physical activity at 21 hours/week. Because no differences in data interpretation were found, the non-truncated physical activity data was used for all analyses.
Covariates
Information collected at baseline also included demographic data (race, household income, education, marital status, age at diagnosis) and physical and behavioral characteristics (body mass index one year before diagnosis, alcohol consumption, smoking status). Treatment and diagnostic characteristics including surgery type, lymph node dissection, receipt of chemotherapy and/or radiation therapy, receipt of hormone therapy, and tumor stage, as well as presence of comorbidities, were abstracted from medical records. The receipt of chemotherapy and/or radiation therapy was coded as chemotherapy only, radiation therapy only, both chemotherapy and radiation therapy, and neither chemotherapy nor radiation therapy. Those who received chemotherapy and hormonal therapy or radiation therapy and hormonal therapy were coded as having received hormonal therapy.
Statistical Analyses
Physical activity levels were described using means (with 95% confidence intervals) and proportions, for the continuous and categorical outcomes, respectively. Covariates were described with proportions. Stratified analyses were restricted to African-American and white women; analysis of the total population included all races. Logistic regression was performed to calculate the odds of insufficient or sedentary versus sufficient post-diagnosis activity by race. Analysis of variance (ANOVA) models were fit to compare post-diagnosis physical activity and mean change in physical activity after diagnosis by study variables. All analyses were weighted by or adjusted for age and race, to account for sampling design as appropriate. The sampling weights were based on four age-race strata: African-American women less than 50 years of age, African-American women aged 50 years or higher, non-African-American women less than 50 years of age, and non-African-American women aged 50 years or higher. Fully adjusted models for both the logistic regression and ANOVA analyses included adjustment for personal characteristics (age at diagnosis, income, education level, marital status, body mass index, alcohol consumption, smoking status, and comorbidities) and treatment- and diagnostic-related variables (stage, receipt of chemotherapy and/or radiation therapy, receipt of hormonal therapy, surgery type, and lymph node removal). Total MET-hours of pre-diagnosis activity were adjusted for in models of post-diagnosis activity. A p-value <.05 was considered statistically significant. SAS version 9.2 (Cary, NC) was used to conduct all analyses.
This study was approved by the Office of Human Research Ethics at the University of North Carolina at Chapel Hill; all patients gave informed consent.
Results
Of the 2,843 breast cancer patients screened for study eligibility and with data available at the time of study analysis, 1,108 were excluded for failure to meet inclusion criteria (n=364), refusal to participate (n=535), non-response (n=178), or for being deceased at the time of contact (n=31); the overall response rate was 71%. The final study population consisted of 1,735 participants, with a weighted mean age at diagnosis of 55.9. Approximately 48% of the participants were African-American. After taking into account weighting, African-American women were more likely to report low incomes, to be diagnosed at less than 50 years of age, and to be diagnosed with stage 3 or 4 breast cancer than white women, but were less likely to receive hormonal therapy (Table 1).
Table 1.
CBCS Totala
|
White
|
African-American
|
||||
---|---|---|---|---|---|---|
N | Weighted % | N | Weighted % | N | Weighted % | |
Total | 1,735 | 859 | 830 | |||
Age at Diagnosis | ||||||
<50 | 851 | 29.1 | 424 | 26.8 | 397 | 35.5 |
≥50 | 884 | 70.9 | 435 | 73.2 | 433 | 64.5 |
Missing | - | |||||
Income | ||||||
<$30,000 | 560 | 28.7 | 161 | 22.3 | 384 | 50.7 |
≥$30,000 | 1,076 | 71.3 | 652 | 77.7 | 396 | 49.3 |
Missing | 99 | 46 | 50 | |||
Educationb | ||||||
< High School | 146 | 7.6 | 43 | 5.9 | 96 | 12.4 |
HS Graduate | 560 | 33.7 | 243 | 33.1 | 304 | 37.5 |
≥ Some College | 1,028 | 58.6 | 573 | 61.0 | 429 | 50.1 |
Missing | 1 | - | 1 | |||
AJCC Stage | ||||||
1 or 2 | 1339 | 84.5 | 693 | 85.9 | 610 | 78.8 |
3 or 4 | 296 | 15.5 | 124 | 14.1 | 165 | 21.2 |
Missing | 100 | 42 | 55 | |||
CT/RTc, d | ||||||
CT and RT | 211 | 14.2 | 88 | 13.2 | 119 | 18.3 |
CT only | 741 | 50.8 | 350 | 49.8 | 374 | 56.7 |
RT only | 126 | 12.1 | 70 | 12.4 | 49 | 8.5 |
No CT or RT | 261 | 22.9 | 152 | 24.6 | 102 | 16.5 |
Missing | 132 | 50 | 79 | |||
Hormonal Therapyd | ||||||
Yes | 459 | 34.2 | 269 | 37.0 | 178 | 24.5 |
No | 1,143 | 65.8 | 537 | 63.0 | 576 | 75.5 |
Missing | 133 | 53 | 76 | |||
Surgeryd | ||||||
Biopsy Only | 148 | 6.2 | 57 | 5.2 | 90 | 10.8 |
Lumpectomy | 525 | 35.5 | 259 | 35.6 | 246 | 33.1 |
Mastectomy | 946 | 58.3 | 495 | 59.2 | 428 | 56.1 |
Missing | 116 | 48 | 66 | |||
Lymph Nodesd | ||||||
≥ 1 LN Removed | 739 | 49.5 | 364 | 45.0 | 357 | 47.8 |
No LNs Removed | 850 | 50.5 | 435 | 55.0 | 392 | 52.2 |
Missing | 146 | 60 | 81 |
Abbreviatons: CBCS = Carolina Breast Cancer Study; HS = High School; AJCC = American Joint Commission on Cancer; CT = Chemotherapy; RT= Radiation Therapy; LN = Lymph Nodes
Total includes all races
The high school graduate category includes those who went to technical school.
For the CT/RT variable: N = 1,474 for total CBCS population, 710 for whites, and 723 for African-Americans
Those who received treatments after post-diagnosis physical activity was assessed were coded as not having received treatment
Table 2 shows level of reported physical activity overall and stratified by race. The average pre- to post-diagnosis reduction in weekly physical activity for the total study population was 15 MET-hours per week (95% CI: 12, 19), with the majority of participants reporting declines in physical activity. There were racial differences in reported levels of activity. African-American women reported lower levels of pre-diagnosis physical activity compared with white women and a larger decline between pre- and post-diagnosis activity. However, a similar percentage of African-American and white women reported a decrease in physical activity levels (60% vs. 59%). In fully adjusted models (adjusting for age at diagnosis, race, income, education level, marital status, body mass index, alcohol consumption, smoking status, comorbidities, stage, receipt of chemotherapy and/or radiation, receipt of hormonal therapy, surgery type, removal of lymph nodes, and pre-diagnosis activity [for the post-diagnosis analysis]), racial differences in post-diagnosis activity and change in activity were not significant (data not shown). African-American women reported 12 MET-hours of post-diagnosis activity versus 14 MET-hours reported by white women (p-value=0.13), and African-American patients reduced their pre-diagnosis activity by 17 MET-hours, while white patients reported an average 16 MET-hour reduction (p-value=0.33).
Table 2.
Total CBCS Populationc | |||||||
---|---|---|---|---|---|---|---|
| |||||||
Pre-diagnosis | Post-diagnosis | Change between pre- and post-diagnosis | |||||
N | Mean (95% CI) | N | Mean (95% CI) | N | Mean (95% CI) | ||
Total minutes | 1,728 | 473.9 (434.0, 513.7) | 1,731 | 245.0 (214.9, 275.2) | 1,726 | −230.3 (−270.4, −190.1) | |
Total METsd | 1,728 | 31.6 (28.9, 34.2) | 1,731 | 16.3 (14.3, 18.3) | 1,726 | −15.4 (−18.0, −12.7) | |
N | (%) | N | (%) | N | (%) | ||
Sedentaryf | 299 | 16.4 | 786 | 42.2 | Increasede | 284 | 17.5 |
Insufficiently activef | 403 | 22.9 | 415 | 23.2 | Decreasede | 1,045 | 59.1 |
Sufficiently activef | 1,025 | 60.6 | 530 | 34.6 | No changee | 397 | 23.4 |
White
| |||||||
---|---|---|---|---|---|---|---|
Pre-diagnosis | Post-diagnosis | Change between pre- and post-diagnosis | |||||
N | Mean (95% CI) | N | Mean (95% CI) | N | Mean (95% CI) | ||
Total minutes | 856 | 491.0 (446.5, 535.6) | 859 | 263.8 (235.7, 291.8) | 856 | −229.1 (−271.7, −186.5) | |
Total METs | 856 | 32.7 (29.8, 35.7) | 859 | 17.6 (15.7, 19.5) | 856 | −15.3 (−18.1, −12.4) | |
N | (%) | N | (%) | N | (%) | ||
Sedentary | 133 | 15.2 | 327 | 39.2 | Increased | 157 | 18.1 |
Insufficiently active | 186 | 22.6 | 209 | 23.2 | Decreased | 518 | 59.1 |
Sufficiently active | 536 | 62.1 | 323 | 37.6 | No change | 181 | 22.8 |
African-American
| |||||||
---|---|---|---|---|---|---|---|
Pre-diagnosis | Post-diagnosis | Change between pre- and post-diagnosis | |||||
N | Mean (95% CI) | N | Mean (95% CI) | N | Mean (95% CI) | ||
Total minutes | 826 | 420.1 (374.8, 465.4) | 827 | 144.7 (116.2, 173.3) | 825 | −275.0 (−318.4, −231.6) | |
Total METs | 826 | 28.0 (25.0, 31.0) | 827 | 9.6 (7.7, 11.6) | 825 | −18.3 (−21.2, −15.4) | |
N | (%) | N | (%) | N | (%) | ||
Sedentary | 154 | 19.2 | 437 | 52.7 | Increased | 121 | 15.1 |
Insufficiently active | 208 | 25.1 | 195 | 23.3 | Decreased | 503 | 60.3 |
Sufficiently active | 464 | 55.7 | 195 | 24.0 | No change | 201 | 24.6 |
Post-diagnosis physical activity was reported, on average, 6 months after diagnosis
All analyses in Table 2 are weighted or adjusted to take into account sampling
Total includes all races
To calculate total METs, MET values of 4.0 and 8.0 were assigned to moderate- and vigorous-intensity activity, were multiplied by reported number of hours per week for each activity type and then were summed
To evaluate change between pre- and post-diagnosis activity, the categorical variable was defined as follows: Increased: increased activity by ≥ 30 minutes compared to pre-diagnosis amount; Decreased: decreased activity by ≥ 30 minutes; No change: reported activity levels at post-diagnosis were within 30 minutes of pre-diagnosis levels
Sedentary = No activity reported; Insufficiently active >0 minutes but < 150 minutes of activity per week; Sufficiently active ≥ 150 minutes of activity per week
In a logistic regression model that was used to examine post-diagnosis physical activity level by race, African-American women had elevated odds of reporting insufficient or sedentary behavior compared to white women, after full adjustment for all of the covariates listed above [odds ratio (OR): 1.38; 95% confidence interval (CI): 1.01, 1.88].
Table 3 shows means for post-diagnosis physical activity levels and for change in activity levels adjusted for all of the listed covariates and stratified by race. Among African-American women, receipt of chemotherapy and/or radiation was significantly associated with post-diagnosis physical activity (p-value <0.01), with those receiving chemotherapy only and those receiving neither chemotherapy nor radiation therapy exercising the least. African-American women who reported no prior comorbidities reduced their post-diagnosis activity to a greater extent than those with comorbidities (p-value=0.04), and though not statistically significant, higher income African-American women reduced their post-diagnosis activity to a lesser extent than those with lower income (p-value=0.06). Among white women, no variable was significantly associated with post-diagnosis physical activity; however, women who were normal or overweight reported higher activity levels than obese women (p-value=0.06). Income (p-value=0.02) and receipt of treatment (p-value=0.02) were significantly associated with change in activity levels, with low income women and women who received neither chemotherapy nor radiation therapy reporting the greatest average reductions in activity.
Table 3.
White N | African-American N | Total MET-Hours of Weekly Physical Activity | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Post-Diagnosis | Mean Change in Activity | |||||||||||||
White | African-American | White | African-American | |||||||||||
Mean | Fully Adjustedb 95% CI | P | Mean | Fully Adjustedb 95% CI | P | Mean | Fully Adjustedb 95% CI | P | Mean | Fully Adjustedb 95% CI | P | |||
Age at Diagnosis | 0.64 | 0.85 | 0.47 | 0.83 | ||||||||||
≥50 | 435 | 433 | 17.5 | (11.7, 23.3) | 11.5 | (6.9, 16.1) | −11.9 | (−22.6, −1.2) | −19.0 | (−28.9, −9.1) | ||||
<50 | 424 | 394 | 16.5 | (10.4, 22.6) | 11.2 | (6.6, 15.8) | −9.2 | (−20.3, 2) | −19.8 | (−29.8, −9.9) | ||||
Income | 0.44 | 0.25 | 0.02 | 0.06 | ||||||||||
<$30,000 | 161 | 383 | 15.9 | (9.7, 22) | 10.2 | (5.9, 14.5) | −16.5 | (−27.7, −5.2) | −23.3 | (−32.6, −13.9) | ||||
≥$30,000 | 652 | 395 | 18.1 | (11.7, 24.5) | 12.4 | (7.5, 17.4) | −4.6 | (−16.3, 7.1) | −15.6 | (−26.3, −4.9) | ||||
Education | 0.73 | 0.35 | 0.91 | 0.21 | ||||||||||
< High School | 43 | 95 | 14.9 | (5.1, 24.7) | 14.0 | (7.5, 20.5) | −9.0 | (−27.1, 9.1) | −12.0 | (−26, 2) | ||||
HS Graduate | 243 | 304 | 17.5 | (11.7, 23.2) | 9.5 | (4.9, 14.2) | −12.1 | (−22.6, −1.6) | −23.2 | (−33.3, −13.1) | ||||
≥ Some College | 573 | 428 | 18.6 | (12.9, 24.2) | 10.5 | (6.1, 14.8) | −10.6 | (−21, −0.2) | −23.0 | (−32.4, −13.7) | ||||
Marital Status | 0.53 | 0.12 | 0.32 | 0.57 | ||||||||||
Single | 42 | 159 | 16.3 | (6.3, 26.4) | 10.0 | (4.7, 15.4) | −11.6 | (−30, 6.8) | −18.8 | (−30.4, −7.3) | ||||
Widowed | 59 | 72 | 16.5 | (7.9, 25) | 10.1 | (3.4, 16.8) | −8.1 | (−23.7, 7.6) | −22.7 | (−37.3, −8.2) | ||||
Divorced/Separated | 153 | 250 | 19.5 | (13, 25.9) | 10.5 | (5.7, 15.4) | −7.0 | (−18.8, 4.8) | −20.8 | (−31.3, −10.3) | ||||
Married | 605 | 346 | 15.6 | (10.1, 21.1) | 14.6 | (10.1, 19.2) | −15.5 | (−25.7, −5.4) | −15.3 | (−25.2, −5.4) | ||||
Body Mass Index | 0.06 | 0.60 | 0.05 | 0.48 | ||||||||||
Obese | 272 | 473 | 13.6 | (7.4, 19.9) | 10.9 | (6.5, 15.4) | −4.5 | (−15.9, 6.9) | −16.7 | (−26.4, −7.1) | ||||
Overweight | 260 | 224 | 18.3 | (12.1, 24.5) | 12.6 | (7.7, 17.5) | −12.8 | (−24.2, −1.5) | −21.6 | (−32.2, −11) | ||||
Normal | 319 | 129 | 19.0 | (12.9, 25.2) | 10.4 | (4.9, 15.9) | −14.3 | (−25.6, −3) | −19.9 | (−31.8, −8) | ||||
Alcohol Consumption | 0.59 | 0.39 | 0.14 | 0.28 | ||||||||||
Ever Use | 734 | 597 | 16.1 | (10.7, 21.6) | 12.2 | (8, 16.4) | −14.7 | (−24.7, −4.6) | −17.2 | (−26.3, −8.1) | ||||
Never Use | 125 | 230 | 17.8 | (10.7, 24.9) | 10.5 | (5.4, 15.6) | −6.4 | (−19.5, 6.6) | −21.6 | (−32.5, −10.7) | ||||
Smoking Status | 0.98 | 0.82 | 0.41 | 0.27 | ||||||||||
Ever Smoked | 411 | 344 | 17.0 | (10.9, 23) | 11.5 | (6.9, 16.2) | −9.0 | (−20.1, 2.1) | −21.6 | (−31.6, −11.5) | ||||
Never Smoked | 448 | 483 | 17.0 | (11.2, 22.7) | 11.1 | (6.6, 15.7) | −12.1 | (−22.7, −1.4) | −17.3 | (−27.1, −7.4) | ||||
Comorbidities | 0.12 | 0.86 | 0.24 | 0.04 | ||||||||||
Yes | 629 | 645 | 15.2 | (9.8, 20.6) | 11.5 | (7.4, 15.6) | −13.0 | (−23, −3.1) | −14.4 | (−23.3, −5.6) | ||||
No | 192 | 132 | 18.8 | (12.2, 25.3) | 11.1 | (5.7, 16.5) | −8.1 | (−20.1, 4) | −24.4 | (−36.1, −12.8) | ||||
AJCC Stage | 0.75 | 0.73 | 0.39 | 0.22 | ||||||||||
1 or 2 | 693 | 609 | 16.5 | (11.1, 22) | 11.7 | (7.5, 15.9) | −8.3 | (−18.3, 1.6) | −16.5 | (−25.6, −7.5) | ||||
3 or 4 | 124 | 163 | 17.4 | (10.5, 24.3) | 11.0 | (5.7, 16.2) | −12.8 | (−25.5, −0.1) | −22.3 | (−33.7, −10.9) | ||||
CT/RTc | 0.13 | <0.01 | 0.02 | 0.38 | ||||||||||
CT and RT | 88 | 119 | 19.3 | (12.2, 26.4) | 10.2 | (5.3, 15.1) | −2.4 | (−15.4, 10.6) | −16.1 | (−26.7, −5.6) | ||||
CT only | 350 | 173 | 14.9 | (8.9, 20.9) | 7.2 | (2.5, 11.8) | −15.0 | (−26, −4) | −16.3 | (−26.4, −6.2) | ||||
RT only | 70 | 49 | 20.4 | (12.2, 28.6) | 19.4 | (12, 26.8) | −5.0 | (−20.1, 10) | −19.0 | (−35, −3.1) | ||||
No CT or RT | 152 | 101 | 13.2 | (6.4, 20.1) | 8.5 | (2.8, 14.2) | −19.8 | (−32.4, −7.2) | −26.2 | (−38.4, −13.9) | ||||
Hormonal Therapyc | 0.21 | 0.48 | 0.69 | 0.06 | ||||||||||
Yes | 269 | 177 | 19.0 | (11.9, 26.1) | 12.4 | (6.2, 18.5) | −9.4 | (−22.5, 3.7) | −13.5 | (−26.8, −0.2) | ||||
No | 537 | 574 | 14.9 | (9.3, 20.6) | 10.3 | (6.4, 14.2) | −11.7 | (−22.2, −1.3) | −25.3 | (−33.8, −16.9) | ||||
Surgeryc | 0.85 | 0.69 | 0.70 | 0.11 | ||||||||||
Biopsy | 57 | 90 | 17.2 | (8.8, 25.7) | 12.5 | (6.1, 18.9) | −9.6 | (−25.1, 5.9) | −10.8 | (−24.7, 3.1) | ||||
Lumpectomy | 259 | 246 | 16.2 | (9.7, 22.7) | 10.1 | (5.1, 15) | −9.4 | (−21.2, 2.5) | −24.9 | (−35.5, −14.2) | ||||
Mastectomy | 495 | 425 | 17.5 | (11.9, 23.1) | 11.4 | (7.2, 15.6) | −12.7 | (−22.9, −2.5) | −22.6 | (−31.6, −13.6) | ||||
Lymph Nodesc | 0.58 | 0.60 | 0.25 | 0.17 | ||||||||||
≥ 1 LN Removed | 364 | 354 | 16.4 | (10.3, 22.5) | 11.9 | (6.9, 16.8) | −8.3 | (−19.5, 2.9) | −16.4 | (−27.1, −5.8) | ||||
No LNs Removed | 435 | 392 | 17.6 | (11.7, 23.4) | 10.8 | (6.4, 15.2) | −12.8 | (−23.4, −2.1) | −22.4 | (−31.9, −12.8) |
Abbreviatons: CI= Confidence Interval; HS = High School; AJCC = American Joint Commission on Cancer; CT = Chemotherapy; RT= Radiation Therapy; LN = Lymph Nodes
Post-diagnosis physical activity was reported, on average, 6 months after diagnosis
Fully adjusted models include adjustment for total minutes of pre-diagnosis physical activity, in addition to all of the listed covariates
Treatment-related variables includes only those who treatment regimens began before post-diagnosis physical activity was assessed
Discussion
Our study found that physical activity declined on average by 15 MET-hours/week between pre- and post-breast cancer diagnosis. Further, approximately 65% of the women failed to meet national recommendations for physical activity levels following a breast cancer diagnosis, compared to 39% pre-diagnosis. Compared with white women, we found that African-American women were less likely to meet national physical activity guidelines, reported lower amounts of pre- and post-diagnosis activity, and reported larger declines in physical activity between pre- and post-breast cancer diagnosis, though differences in post-diagnosis activity and change in activity levels were not statistically significant in multivariate analyses.
Overall, our findings are consistent with those reported in previous studies,18–20 though the magnitude of decline in physical activity reported here are greater than in previous findings. The inclusion of physical activity reported soon after breast cancer diagnosis for some participants, where larger reductions in physical activity occurred (in our study, the average time was 6 months post-diagnosis), may partially explain the difference in magnitude between our results and previous studies. Our findings of potential racial differences among breast cancer survivors are also consistent with results from previous studies.1, 22 In a racially diverse study of breast cancer survivors, African-American women (n=118) had the lowest value of reported median MET-minutes/week at 225.0 (whites [n=2,634] reported a median value of 607.5) and were less likely than other racial groups to meet physical activity guidelines post-diagnosis.1 Specifically, 32% of African-Americans reported meeting physical activity guidelines, which is higher than the 24% who reported meeting the guidelines in our study.1 The multi-ethnic HEAL study, also reported that African-Americans were less likely to meet the physical activity recommendations compared to whites and Hispanics, with 23% of African-Americans (n= 259) meeting the guidelines when reporting on sports and/or recreational physical activity, though the percentage increased to 63% when all types of physical activity were included.22
Findings from focus groups conducted with African-American breast cancer survivors may provide clues for the inadequate physical activity levels specifically reported by this subgroup.28, 29 African-American women in one study indicated that while they were aware of the benefits of exercise, those who reported a higher income were more knowledgeable of the potential benefits and more likely to engage in regular physical activity.29 Though not statistically significant, our results showing that low income African-American women were more likely to report higher declines in physical post-diagnosis support these findings. Another focus group of African-American breast cancer survivors found that only 21% mentioned physical activity as a strategy to reduce risk of recurrence and that many participants did not receive physical activity guidelines from healthcare providers.28
Type of treatment received also seems to impact activity levels in breast cancer patients. Our fully-adjusted stratified results suggested that the administration of adjuvant therapy, and the type of therapy received, may be associated with post-diagnosis physical activity levels in African-American women and with change in activity levels in white women. Interestingly, both receipt of chemotherapy alone and no receipt of chemotherapy or radiation therapy were associated with lower physical activity levels and higher declines in physical activity post-diagnosis. It seems plausible that side effects associated with receipt of chemotherapy, such as pain, fatigue or neuropathy, may present as barriers to engaging in physical activity.29 In contrast, lack of receipt of adjuvant therapy may reduce contact with health professionals who may promote and encourage participation in physical activity during and beyond breast cancer treatment. Additional work is needed to more precisely sort out potential determinants.
Of note, our findings also suggested that approximately one in five women increased their activity levels by at least 30 minutes a week after being diagnosed with breast cancer. Understanding motivations for positive change in physical activity would prove useful in designing interventions to promote exercise among breast cancer patients. Current research indicates that both the distribution of pedometers 30 and the sense of accomplishment that comes with being physically activity during cancer treatment 31 have been motivating factors for increasing post-diagnosis activity levels. One report suggested that among African-American women, home-based exercise programs have also led to increased post-diagnosis physical activity levels. 32 In our dataset, women who increased versus decreased post-diagnosis activity were more likely to report high income, receipt of radiation therapy only versus chemotherapy only, and receipt of hormonal therapy (data not shown), suggesting that income level and type of therapy received should also be considered in the design of interventions. More research is warranted to determine what other characteristics are associated with increased post-diagnosis physical activity.
Our findings were derived from a population-based study and our sampling design was successful at recruiting a large proportion of African-American women with breast cancer, allowing for adequately powered subgroup analysis. Nonetheless, this work may be limited by non-response. Our response rates were moderate (71% overall, 67% for African-American women, and 74% for white women) and, within the racial groups, there was no difference in mean age for those who did and did not participate in the study. However, it is possible that breast cancer patients who participate in the study are highly motivated individuals who may be more likely to exercise than non-participants. Women in our study were more likely to meet physical activity guidelines pre-diagnosis than women in the 2011 US population (61% vs. 46%),33 suggesting potential overestimation of physical activity levels in our data when compared to the general population.
This work may also be limited by the retrospective data collection of pre-diagnosis physical activity levels. It is unclear what impact distant recall of physical activity has on the validity of reported levels, with some studies finding only modest correlations between activity reported in the past and later recall of that same activity,34, 35 and other research reporting higher correlations.36 There is evidence that the accuracy of the recall of past activity levels differs by the activity type,35, 36 with one study finding that individuals tend to overestimate prior vigorous activity and underestimate prior light and moderate activity.35 Therefore, it is difficult to predict whether the levels of activity reported in our analyses over- or underestimate the true levels of physical activity in our study population. Similarly, it is difficult to predict how recall might differ between the reporting of pre-diagnosis physical activity (in which participants were asked to recall weekly activity 3 months prior to diagnosis) and the reporting of post-diagnosis activity (in which participants were asked to report activity in the week prior to their baseline interview). It is possible that the post-diagnosis physical activity variable is less prone to measurement error than the change in activity variable because the latter required more distant recall.
Additionally, there is evidence that survivors’ level of activity changes dependent on the amount of time that has passed since the diagnosis, with one study finding that those further out from diagnosis have higher activity levels than those closer to diagnosis20 and another study reporting the opposite.17 In our study, though study participants reported their physical activity, on average, 6 months post-diagnosis, the range was from 1.8 to 32.8 months post-diagnosis, with 95% of all interviews occurring within 12 months of diagnosis. We conducted a sensitivity analysis restricted to those whose physical activity was assessed within the first year after diagnosis, and found no meaningful changes in our overall study estimates or interpretation, though the p-value for the odds ratio comparing post-diagnosis activity between African-Americans and whites increased from .05 to .07.
It has been suggested that exercise needs to be formally incorporated into the care of women with breast cancer. A recently proposed breast cancer care model recommended that patients be educated about physical activity at the point of breast cancer diagnosis, and be provided with the necessary support and advice to become and stay active along the breast cancer diagnosis-treatment continuum and beyond.11 Our findings, which clearly demonstrate that the majority of breast cancer survivors remain insufficiently active or sedentary post-diagnosis and are likely to reduce physical activity between pre- and post-diagnosis, further highlight the potential for change and the value that implementation of such a model could bring. Though breast cancer advocates are actively promoting the message that physical activity post-diagnosis improves quality of life and survival, and the evidence supporting participation in physical activity following breast cancer continues to mount, it is clear that more work needs to be done to translate evidence into practice, especially among African-American women.
Acknowledgments
Funding Sources:
This research was funded in part by the University Cancer Research Fund of North Carolina and the National Cancer Institute Specialized Program of Research Excellence (SPORE) in Breast Cancer (NIH/NCI P50-CA58223). The research position of Dr Sandi Hayes is supported by the National Breast Cancer Foundation of Australia.
Footnotes
There are no financial disclosures from any of the authors.
References
- 1.Paxton RJ, Phillips KL, Jones LA, et al. Associations among physical activity, body mass index, and health-related quality of life by race/ethnicity in a diverse sample of breast cancer survivors. Cancer. 2012 doi: 10.1002/cncr.27389. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Smith AW, Alfano CM, Reeve BB, et al. Race/ethnicity, physical activity, and quality of life in breast cancer survivors. Cancer Epidemiol Biomarkers Prev. 2009;18:656–663. doi: 10.1158/1055-9965.EPI-08-0352. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Mandelblatt JS, Luta G, Kwan ML, et al. Associations of physical activity with quality of life and functional ability in breast cancer patients during active adjuvant treatment: The pathways study. Breast Cancer Res Treat. 2011;129:521–529. doi: 10.1007/s10549-011-1483-5. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Schwartz AL, Mori M, Gao R, Nail LM, King ME. Exercise reduces daily fatigue in women with breast cancer receiving chemotherapy. Med Sci Sports Exerc. 2001;33:718–723. doi: 10.1097/00005768-200105000-00006. serial online. [DOI] [PubMed] [Google Scholar]
- 5.Beasley JM, Kwan ML, Chen WY, et al. Meeting the physical activity guidelines and survival after breast cancer: Findings from the after breast cancer pooling project. Breast Cancer Res Treat. 2012;131:637–643. doi: 10.1007/s10549-011-1770-1. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Ballard-Barbash R, Friedenreich CM, Courneya KS, Siddiqi SM, McTiernan A, Alfano CM. Physical activity, biomarkers, and disease outcomes in cancer survivors: A systematic review. J Natl Cancer Inst. 2012 doi: 10.1093/jnci/djs207. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Holick CN, Newcomb PA, Trentham-Dietz A, et al. Physical activity and survival after diagnosis of invasive breast cancer. Cancer Epidemiol Biomarkers Prev. 2008;17:379–386. doi: 10.1158/1055-9965.EPI-07-0771. serial online. [DOI] [PubMed] [Google Scholar]
- 8.Sternfeld B, Weltzien E, Quesenberry CP, Jr, et al. Physical activity and risk of recurrence and mortality in breast cancer survivors: Findings from the LACE study. Cancer Epidemiol Biomarkers Prev. 2009;18:87–95. doi: 10.1158/1055-9965.EPI-08-0595. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Ibrahim EM, Al-Homaidh A. Physical activity and survival after breast cancer diagnosis: Meta-analysis of published studies. Med Oncol. 2011;28:753–765. doi: 10.1007/s12032-010-9536-x. serial online. [DOI] [PubMed] [Google Scholar]
- 10.Irwin ML, Smith AW, McTiernan A, et al. Influence of pre- and postdiagnosis physical activity on mortality in breast cancer survivors: The Health, Eating, Activity, and Lifestyle study. J Clin Oncol. 2008;26:3958–3964. doi: 10.1200/JCO.2007.15.9822. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Stout NL, Binkley JM, Schmitz KH, et al. A prospective surveillance model for rehabilitation for women with breast cancer. Cancer. 2012;118:2191–2200. doi: 10.1002/cncr.27476. serial online. [DOI] [PubMed] [Google Scholar]
- 12.Hayes SC, Johansson K, Stout NL, et al. Upper-body morbidity after breast cancer: Incidence and evidence for evaluation, prevention, and management within a prospective surveillance model of care. Cancer. 2012;118:2237–2249. doi: 10.1002/cncr.27467. serial online. [DOI] [PubMed] [Google Scholar]
- 13.Hayes S, Johansson K, Alfano CM, Schmitz KH. Exercise for breast cancer survivors: Bridging the gap between evidence and practice. Translational Behavioral Medicine. 2011;1:539. doi: 10.1007/s13142-011-0082-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.US Department of Health and Human Services. Physical Activity Guidelines for Americans. 2012 Available from URL: http://www.health.gov/paguidelines/guidelines/summary.aspx.
- 15.American Cancer Society. ACS Guidelines on Nutrition and Physical Activity for Cancer Prevention. 2012 Available from URL: http://www.cancer.org/acs/groups/cid/documents/webcontent/002577-pdf.pdf.
- 16.Rock CL, Doyle C, Demark-Wahnefried W, et al. Nutrition and physical activity guidelines for cancer survivors. CA Cancer J Clin. 2012;62:243–274. doi: 10.3322/caac.21142. serial online. [DOI] [PubMed] [Google Scholar]
- 17.Mason C, Alfano CM, Smith AW, et al. Long-term physical activity trends in breast cancer survivors. Cancer Epidemiol Biomarkers Prev. 2013;22:1153–1161. doi: 10.1158/1055-9965.EPI-13-0141. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Kwan ML, Sternfeld B, Ergas IJ, et al. Change in physical activity during active treatment in a prospective study of breast cancer survivors. Breast Cancer Res Treat. 2012;131:679–690. doi: 10.1007/s10549-011-1788-4. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Harrison S, Hayes SC, Newman B. Level of physical activity and characteristics associated with change following breast cancer diagnosis and treatment. Psychooncology. 2009;18:387–394. doi: 10.1002/pon.1504. serial online. [DOI] [PubMed] [Google Scholar]
- 20.Littman AJ, Tang MT, Rossing MA. Longitudinal study of recreational physical activity in breast cancer survivors. J Cancer Surviv. 2010;4:119–127. doi: 10.1007/s11764-009-0113-2. serial online. [DOI] [PubMed] [Google Scholar]
- 21.Irwin ML, Crumley D, McTiernan A, et al. Physical activity levels before and after a diagnosis of breast carcinoma: The Health, Eating, Activity, and Lifestyle (HEAL) study. Cancer. 2003;97:1746–1757. doi: 10.1002/cncr.11227. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Irwin ML, McTiernan A, Bernstein L, et al. Physical activity levels among breast cancer survivors. Med Sci Sports Exerc. 2004;36:1484–1491. serial online. [PMC free article] [PubMed] [Google Scholar]
- 23.Adams SA, Butler WM, Fulton J, et al. Racial disparities in breast cancer mortality in a multiethnic cohort in the southeast. Cancer. 2012;118:2693–2699. doi: 10.1002/cncr.26570. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Whitman S, Orsi J, Hurlbert M. The racial disparity in breast cancer mortality in the 25 largest cities in the united states. Cancer Epidemiol. 2012;36:e147–51. doi: 10.1016/j.canep.2011.10.012. serial online. [DOI] [PubMed] [Google Scholar]
- 25.McGee SA, Durham DD, Tse CK, Millikan RC. Determinants of breast cancer treatment delay differ for African American and white women. Cancer Epidemiol Biomarkers Prev. 2013;22:1227–1238. doi: 10.1158/1055-9965.EPI-12-1432. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Centers for Disease Control and Prevention (CDC) Behavioral risk factor surveillance system survey questionnaire. 2001. [Google Scholar]
- 27.International Physical Activity Questionnaire. Guidelines for data processing and analysis of the international physical activity guidelines. 2012 Available from URL: https://sites.google.com/site/theipaq/home. [PubMed]
- 28.Royak-Schaler R, Passmore SR, Gadalla S, et al. Exploring patient-physician communication in breast cancer care for African American women following primary treatment. Oncol Nurs Forum. 2008;35:836–843. doi: 10.1188/08.ONF.836-843. serial online. [DOI] [PubMed] [Google Scholar]
- 29.Stolley MR, Sharp LK, Wells AM, Simon N, Schiffer L. Health behaviors and breast cancer: Experiences of urban African American women. Health Educ Behav. 2006;33:604–624. doi: 10.1177/1090198106290845. serial online. [DOI] [PubMed] [Google Scholar]
- 30.Vallance JK, Courneya KS, Plotnikoff RC, Yasui Y, Mackey JR. Randomized controlled trial of the effects of print materials and step pedometers on physical activity and quality of life in breast cancer survivors. J Clin Oncol. 2007;25:2352–2359. doi: 10.1200/JCO.2006.07.9988. serial online. [DOI] [PubMed] [Google Scholar]
- 31.Blaney J, Lowe-Strong A, Rankin J, Campbell A, Allen J, Gracey J. The cancer rehabilitation journey: Barriers to and facilitators of exercise among patients with cancer-related fatigue. Phys Ther. 2010;90:1135–1147. doi: 10.2522/ptj.20090278. serial online. [DOI] [PubMed] [Google Scholar]
- 32.Spector D, Deal AM, Amos KD, Yang H, Battaglini CL. A pilot study of a home-based motivational exercise program for African American breast cancer survivors: Clinical and quality-of-life outcomes. Integr Cancer Ther. 2013 doi: 10.1177/1534735413503546. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Go AS, Mozaffarian D, Roger VL, et al. Heart disease and stroke statistics--2013 update: A report from the American Heart Association. Circulation. 2013;127:e6–e245. doi: 10.1161/CIR.0b013e31828124ad. serial online. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Blair SN, Dowda M, Pate RR, et al. Reliability of long-term recall of participation in physical activity by middle-aged men and women. Am J Epidemiol. 1991;133:266–275. doi: 10.1093/oxfordjournals.aje.a115871. serial online. [DOI] [PubMed] [Google Scholar]
- 35.Falkner KL, Trevisan M, McCann SE. Reliability of recall of physical activity in the distant past. Am J Epidemiol. 1999;150:195–205. doi: 10.1093/oxfordjournals.aje.a009980. serial online. [DOI] [PubMed] [Google Scholar]
- 36.Slattery ML, Jacobs DR., Jr Assessment of ability to recall physical activity of several years ago. Ann Epidemiol. 1995;5:292–296. doi: 10.1016/1047-2797(94)00095-b. serial online. [DOI] [PubMed] [Google Scholar]