Abstract
Introduction:
Progress in U.S. 5-year survival trends for all cancers combined was assessed using the North American Cancer Survival Index (CSI), a sum of age-, sex-, and cancer site–standardized relative survival ratioss.
Methods:
In February 2019, authors calculated 5-year CSIs and 95% CIs by race and sex for 2005–2011, 2006–2012, 2007–2013, and 2008–2014 diagnosis cohorts with data from 42 cancer registries.
Results:
Overall 5-year survival increased from 63.5% (95% CI=63.4%, 63.5%) in 2005–2011 to 64.1% (95% CI=64.1%, 64.2%) in 2008–2014. Survival increased 0.9 and 0.5 percentage points in female and male patients, respectively; the survival disparity among blacks versus whites decreased by 0.5%. In 2008–2014, the CSI was 7.7% higher for whites (64.6%, 95% CI=64.6%, 64.7%) compared with blacks (56.9%, 95% CI=56.7%, 57.1%).
Conclusions:
CSI survival estimates increased among all race and sex subpopulations during 2005–2014. A substantial but decreasing survival gap persisted between blacks and whites. The CSI can assist decision makers and others in comparing cancer survival among populations and over time, and in monitoring progress toward national cancer surveillance objectives.
INTRODUCTION
Cancer is the second leading cause of potentially preventable death in the U.S.,1 and might soon surpass cardiovascular disease as the overall leading cause of death.2 Population-based statistics summarizing cancer survival assess how effectively healthcare systems manage cancer.3 Although site-specific survival estimates provide prognostic indicators for specific cancers, one number summary metrics like all-cancer site survival communicate health systems’ performance to policymakers (e.g., as found in Healthy People 2020), and can be useful in evaluating health disparities at the systems level.4 Population-based metrics of all-cancer sites net survival can, however, mask important differences by age, sex, and primary cancer site.
Since 2008, cancer researchers in Europe have used age- and primary site–standardized survival estimates to evaluate temporal trends and disparities in cancer survival across nations, and subnational administrative areas5,6—approaches less commonly used in North America. The recently described North American Cancer Survival Index (CSI),7 like European population based, age-standardized, and cancer site–standardized relative survival estimates, evaluated survival trends over time, and identified survival disparities by sex and race.
METHODS
All U.S. population-based cancer registries are members of the North American Association of Central Cancer Registries. For inclusion herein, registries provided consent; met Cancer in North America incidence criteria for cancers diagnosed during 2005–2014; and complied with Surveillance, Epidemiology, and End Results (SEER) standards for follow-up or ascertained vital status through linkage with state and National Death Index death records through December 31, 2014. SEER behavior recode for analysis-defined malignant cases diagnosed among people aged 15–99 years during 2005–2014 were included in these analyses.8 Incident cases only reported by autopsy or death certificates, and, among registries meeting SEER follow-up standards, cases with no follow-up time among living patients were excluded. Among patients with multiple primary cancer diagnoses, the earliest diagnosed case for each primary site category was used to estimate survival. The North American Association of Central Cancer Registries and U.S. Centers for Disease Control and Prevention reviewed and approved the secondary analysis of the de-identified data of the study.
The CSI estimates are weighted sums of age-standardized, site-specific relative survival ratios (RSRs), with weights derived from the relative distribution of cancers diagnosed during 2006–2008 in North America; methods are described in detail elsewhere.5,8 In February 2019, authors calculated 5-year age-standardized site-specific RSRs with the complete approach of grouping patients by year of diagnosis and follow-up and the Ederer II method for calculating expected survival rates on age-, sex-, achieved year–, geographic area–, race-, and SES-matched life tables.9,10 Cases were censored at an achieved age of 100 years. RSRs and corresponding SEs were generated with SEER*Stat, version 8.3.5.7 CSIs and 95% CIs were calculated using SAS, version 9.4 using formulas described elsewhere.7,11 CSI point estimates and 95% CIs were compared over time by diagnosis cohorts (2005–2011, 2006–2012, 2007–2013, and 2008–2014), black or white race categories, female or male sex categories, and race–sex category combinations.
RESULTS
These analyses included data from 42 U.S. population-based cancer registries (41 states and one metropolitan area), representing approximately 83% of the U.S. population and >11.9 million cancers. Survival increased steadily over time across diagnosis cohorts, from 63.5% (95% CI=63.4%, 63.5%) of expected survival in 2005–2011, to 63.8% (95% CI=63.7%, 63.8%) in 2006–2012, 64.0% (95% CI=64.0%, 64.1%) in 2007–2013, and 64.1% (95% CI=64.1%, 64.2%) in 2008–2014 (Table 1). From 2005–2011 to 2008–2014, CSI estimates for female and male patients increased by 0.9 and 0.5 percentage points, respectively. Among female patients, survival increased from 63.9% (95% CI=63.9%, 64.0%) in 2005–2011 to 64.8% (95% CI=64.8%, 64.9%) in 2008–2014; among male patients, survival increased from 63.0% (95% CI=63.0%, 63.1%) in 2005–2011 to 63.5% (95% CI=63.4%, 63.6%) in 2008–2014.
Table 1.
Cancer Survival Indexa Overall and by Race and Sex by Cohort
| Diagnosis and follow-up cohort | N | Cancer survival index | 95% CI |
|---|---|---|---|
| Total, female | |||
| 2005–2011 | 3,979,796 | 63.9 | 63.9, 64.0 |
| 2006–2012 | 4,075,570 | 64.3 | 64.2, 64.3 |
| 2007–2013 | 4,140,411 | 64.6 | 64.5, 64.6 |
| 2008–2014 | 4,199,905 | 64.8 | 64.8, 64.9 |
| Total, male | |||
| 2005–2011 | 4,279,643 | 63.0 | 63.0, 63.1 |
| 2006–2012 | 4,351,935 | 63.3 | 63.2, 63.4 |
| 2007–2013 | 4,375,271 | 63.5 | 63.4, 63.6 |
| 2008–2014 | 4,373,694 | 63.5 | 63.4, 63.6 |
| Total, male and female | |||
| 2005–2011 | 8,259,439 | 63.5 | 63.4, 63.5 |
| 2006–2012 | 8,427,505 | 63.8 | 63.7, 63.8 |
| 2007–2013 | 8,515,682 | 64.0 | 64.0, 64.1 |
| 2008–2014 | 8,573,599 | 6.1 | 64.1, 64.2 |
| Black, female | |||
| 2005–2011 | 425,665 | 55.7 | 55.5, 56.0 |
| 2006–2012 | 442,681 | 56.0 | 55.8, 56.3 |
| 2007–2013 | 454,784 | 56.6 | 56.4, 56.9 |
| 2008–2014 | 466,007 | 57.1 | 56.9, 57.4 |
| Black, male | |||
| 2005–2011 | 470,356 | 55.8 | 55.5, 56.2 |
| 2006–2012 | 483,527 | 56.2 | 55.9, 56.6 |
| 2007–2013 | 489,994 | 56.4 | 56.0, 56.7 |
| 2008–2014 | 492,820 | 56.7 | 56.3, 57.0 |
| Black, male and female | |||
| 2005–2011 | 896,021 | 55.8 | 55.6, 56.0 |
| 2006–2012 | 926,208 | 56.1 | 55.9, 56.3 |
| 2007–2013 | 944,778 | 56.5 | 56.3, 56.7 |
| 2008–2014 | 958,827 | 56.9 | 56.7, 57.1 |
| White, female | |||
| 2005–2011 | 3,369,915 | 64.7 | 64.6, 64.7 |
| 2006–2012 | 3,438,378 | 65.0 | 64.9, 65.1 |
| 2007–2013 | 3,480,657 | 65.3 | 65.2, 65.4 |
| 2008–2014 | 3,518,834 | 65.5 | 65.5, 65.6 |
| White, male | |||
| 2005–2011 | 3,620,973 | 63.4 | 63.3, 63.5 |
| 2006–2012 | 3,670,432 | 63.6 | 63.6, 63.7 |
| 2007–2013 | 3,678,455 | 63.8 | 63.7, 63.9 |
| 2008–2014 | 3,667,353 | 63.8 | 63.7, 63.8 |
| White, male and female | |||
| 2005–2011 | 6,990,888 | 64.0 | 64.0, 64.1 |
| 2006–2012 | 7,108,810 | 64.3 | 64.2, 64.3 |
| 2007–2013 | 7,159,112 | 64.5 | 64.5, 64.6 |
| 2008–2014 | 7,186,187 | 64.6 | 64.6, 64.7 |
Cancer Survival Index (CSI) calculated by weighted summing of age-standardized, site-specific relative survival ratios, with weights derived from the relative distribution of cancers diagnosed during 2006–2008 in North America.
The CSI estimates increased monotonically over time among both race categories and all race–sex subpopulations. From 2005–2011 to 2008–2014, the largest absolute survival improvement was reported among black female patients (1.4%), and the smallest absolute survival improvement was reported among white male patients (0.4%). Among whites, there was an absolute survival improvement of 0.6% during the study period, from 64.0% (95% CI=64.0%, 64.1%) in 2005–2011 to 64.6% (95% CI=64.6%, 64.7%) in 2008–2014. Among white male patients, the CSI was 63.4% (95% CI=63.3%, 63.5%) in 2005–2011, and 63.8% (95% CI=63.7%, 63.8%) in 2008–2014. The CSI for white female patients was consistently higher than all other subpopulations during the study period, from 64.7% (95% CI=64.6%, 64.7%) during 2005–2011 to 65.5% (95% CI=65.5%, 65.6%) in 2008–2014.
Among blacks, there was an absolute survival improvement of 1.1% during the study period, from 55.8% (95% CI=55.6%, 56.0%) in 2005–2011 to 56.9% (95% CI=56.7%, 57.1%) in 2008–2014. Among black male patients, there was an absolute CSI increase of 0.8% during the study period, from 55.8% (95% CI=55.5%, 56.2%) in 2005–2011 to 56.7% (95% CI=56.3%, 57.0%) during 2008–2014. Among black female patients, the CSI increased from 55.7% (95% CI=55.5, 56.0%) to 57.1% (95% CI=56.9%, 57.4%) in 2008–2014. Absolute survival disparities between blacks and whites decreased by 0.5% overall from 2005–2011 (−8.2%) to 2008–2014 (−7.7%); and the rate of reduction in disparities increased over time, with a 0.06% absolute reduction between 2005–2011 and 2006–2012, a 0.15% absolute reduction between 2006–2012 and 2007–2013, and a 0.30% absolute reduction between 2007–2013 and 2008–2014 cohorts.
DISCUSSION
Population-based 5-year cancer survival measured with the North American CSI increased slightly during 2005–2014 among all evaluated populations. Although survival disparities decreased, the change in survival disparities was small and large disparities in cancer survival among blacks compared with whites persisted.
The age-, sex-, and primary site–standardized CSI offers improved comparability of estimates over time and among populations, and more accurately reflects survival disparities for all cancers combined by race, compared with unweighted summary statistics, such as the all cancers combined RSR.7 Differences in survival estimates might be influenced by registry follow-up protocols; however, comparisons of survival estimates calculated by different follow-up protocols have yielded mostly small differences among whites and blacks, the races compared herein.
Limitations
Additional CSI limitations discussed elsewhere are also applicable to these analyses.7 CSI estimates are generally more conservative and have smaller SEs than unstandardized estimates, and by weighting estimates the CSI better reflects the importance of survival differences reported among higher incidence cancers (e.g., lung and bronchus, and colon and rectum). One-number summary metrics (e.g., the CSI) are not stage adjusted. Stage at diagnosis is commonly related to healthcare systems performance; adjusting for stage could mask differences in cancer survival driven by access to care.
CONCLUSIONS
National cancer survival goals (e.g., Healthy People 2020) are currently evaluated using an unweighted all sites combined RSR, which is calculated with data from 17 SEER registries available at the time of indicator selection.12 Updating Healthy People 2030 with the CSI offers methodologic improvements over current approaches, and uses the largest and most representative data set available for evaluating U.S. cancer survival.
These findings demonstrate using the CSI to assess national cancer survival goals, including survival disparities, among populations and over time. Furthermore, jurisdictions might use national and subnational Cancer in North America CSI estimates to evaluate their jurisdiction’s overall management of cancer.8
ACKNOWLEDGMENTS
All analyses were performed on previously collected, deidentified data from the North American Association of Central Cancer Registries December 2017 data submission. The authors thank cancer registries in the following jurisdictions for their contribution to the data used in this study: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Detroit, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Mississippi, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Utah, Vermont, Washington, West Virginia, Wisconsin, and Wyoming. Support for cancer registries is provided by the state in which the registry is located. In the U.S., registries also participate in the Surveillance, Epidemiology, and End Results program, the Centers for Disease Control and Prevention’s National Program of Cancer Registries, or both.
This project has been funded in whole or in part with Federal funds from the National Cancer Institute, NIH, HHS, under Contract No. HHSN261201800006I and the Centers for Disease Control and Prevention, HHS, under Cooperative Agreement 1NU58DP006270. B. Morawski and H. Weir are supported by the Centers for Disease Control and Prevention. C. Johnson is supported by the Idaho Hospital Association. The authors thank Rick Firth and Steve Scoppa, Information Management Services, Inc., who prepared the analytic dataset used for this project. They also thank Kristine Bisgard and Kris K. Carter for reviewing this brief and providing helpful comments.
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention or the National Cancer Institute.
Footnotes
No financial disclosures were reported by the authors of this paper.
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