Abstract
This cross-sectional study examines cigarette smoking patterns by demographic and clinical characteristics among patients with lung cancer.
Previous studies reported increases in the proportion of patients in the US and UK with lung cancer who never smoked cigarettes,1,2 but these were based on small sample sizes from hospital data rather than population-based cancer registries. Beginning in 2011, the US Centers for Disease Control and Prevention (CDC) National Program of Cancer Registries supported a comparative effectiveness research project to abstract cigarette smoking history from the medical records of patients.3 Using these population-based data, we examined cigarette smoking patterns by demographic and clinical characteristics among patients with lung cancer.
Methods
We included patients 20 years or older who received a diagnosis from January 2011 to December 2016 of microscopically confirmed malignant lung and bronchus cancer as defined by anatomic site codes (C340-C349).4 Cigarette use at diagnosis was determined by medical record abstraction and was coded as never, current, former, and unknown.3 Data were only included for states and years in which less than 15% of cases had cigarette use status coded as unknown (Alaska, Colorado, Florida, Idaho, Louisiana, North Carolina, and Rhode Island). The cancer registries collected information for all patients with cancer; however, 13 496 patients in the included states and years with unknown cigarette use were excluded from the analysis. We calculated the proportion (prevalence) of cigarette smoking status stratified by sex, age, race/ethnicity, and histology and female-to-male prevalence ratios with their 95% CI. Analyses were conducted using SEER*Stat, version 8.3.6 (National Cancer Institute) and SAS, version 9.4 (SAS Institute). This research project was approved by the CDC institutional review board, which determined that patient consent was not needed for this study because the submitted data were deidentified before they were received by the CDC.
Results
Of 129 309 patients with lung cancer, 47 495 (36.7%), 65 665 (50.8%), and 16 149 (12.5%) were current, former, and never smokers, respectively. The proportion of never-smoking patients with lung cancer was higher in women than in men overall (15.7% vs 9.6%; prevalence ratio, 1.63; 95% CI, 1.58-1.68) and across all age, race/ethnicity, and histology categories (Table 13 and Table 23). By age, the never smoking proportion was highest among individuals aged 20 to 49 years (609 of 2198 women [27.7%] and 387 of 2077 men [18.6%]) and lowest among individuals aged 50 to 64 years (2250 of 17 673 women [12.7%] and 1628 of 19 809 men [8.2%]) (Table 1). By race/ethnicity, the proportions of never smoking among women and men with lung cancer were 13.4% (6757/50 407) and 9.0% (4794/53 300) for White patients, 19.0% (1124/5 905) and 8.6% (705/8173) for Black patients, and 32.6% (1289/3952) and 16.0% (836/5225) for Hispanic patients, respectively. By histology, 6% to 8% of men and women with small cell or squamous cell carcinomas were never smokers compared with 5968 of 30 504 women (19.6%) and 3339 of 28 382 men (11.8%) with adenocarcinoma.
Table 1. Tobacco Use Among Women and Men With Lung Cancer by Age, Race/Ethnicity, and Histology in 7 National Program of Cancer Registries States From 2011 to 2016a.
| Characteristics of patients with lung cancer | Total casesb | Smoker, No. (%) | |||
|---|---|---|---|---|---|
| Ever | Current | Former | Never | ||
| Total | 129 309 | 113 160 (87.5) | 47 495 (36.7) | 65 665 (50.8) | 16 149 (12.5) |
| Women | |||||
| Total | 61 351 | 51 742 (84.3) | 21 990 (35.8) | 29 752 (48.5) | 9609 (15.7) |
| Diagnosis age, y | |||||
| 20-49 | 2198 | 1589 (72.3) | 1094 (49.8) | 495 (22.5) | 609 (27.7) |
| 50-64 | 17 673 | 15 423 (87.3) | 8983 (50.8) | 6440 (36.4) | 2250 (12.7) |
| 65-79 | 31 294 | 26 986 (86.2) | 10 347 (33.1) | 16 639 (53.2) | 4308 (13.8) |
| ≥80 | 10 186 | 7744 (76.0) | 1566 (15.4) | 6178 (60.7) | 2442 (24.0) |
| Race/ethnicityc | |||||
| White | 50 407 | 43 650 (86.6) | 18 248 (36.2) | 25 402 (50.4) | 6757 (13.4) |
| Black | 5905 | 4781 (81.0) | 2391 (40.5) | 2390 (40.5) | 1124 (19.0) |
| Asian/Pacific Islander | 612 | 261 (42.6) | 98 (16.0) | 163 (26.6) | 351 (57.4) |
| American Indian/Alaska Native | 250 | 224 (89.6) | 132 (52.8) | 92 (36.8) | 26 (10.4) |
| Hispanic | 3952 | 2663 (67.4) | 1061 (26.8) | 1602 (40.5) | 1289 (32.6) |
| Histologyd | |||||
| Small cell carcinoma | 9114 | 8559 (93.9) | 4640 (50.9) | 3919 (43.0) | 555 (6.1) |
| Adenocarcinoma | 30 504 | 24 536 (80.4) | 9247 (30.3) | 15 289 (50.1) | 5968 (19.6) |
| Squamous cell carcinoma | 11 820 | 10 915 (92.3) | 4765 (40.3) | 6150 (52.0) | 905 (7.7) |
| Other | 9913 | 7732 (78.0) | 3338 (33.7) | 4394 (44.3) | 2181 (22.0) |
| Men | |||||
| Total | 67 958 | 61 418 (90.4) | 25 505 (37.5) | 35 913 (52.8) | 6540 (9.6) |
| Diagnosis age, y | |||||
| 20-49 | 2077 | 1690 (81.4) | 1139 (54.8) | 551 (26.5) | 387 (18.6) |
| 50-64 | 19 809 | 18 181 (91.8) | 11 204 (56.6) | 6977 (35.2) | 1628 (8.2) |
| 65-79 | 34 878 | 31 798 (91.2) | 11 630 (33.3) | 20 168 (57.8) | 3080 (8.8) |
| ≥80 | 11 194 | 9749 (87.1) | 1532 (13.7) | 8217 (73.4) | 1445 (12.9) |
| Race/ethnicityc | |||||
| White | 53 300 | 48 506 (91.0) | 19 489 (36.6) | 29 017 (54.4) | 4794 (9.0) |
| Black | 8173 | 7468 (91.4) | 3948 (48.3) | 3520 (43.1) | 705 (8.6) |
| Asian/Pacific Islander | 601 | 469 (78.0) | 178 (29.6) | 291 (48.4) | 132 (22.0) |
| American Indian/Alaska Native | 287 | 276 (96.2) | 143 (49.8) | 133 (46.3) | 11 (3.8) |
| Hispanic | 5225 | 4389 (67.4) | 1622 (26.8) | 2767 (40.5) | 836 (32.6) |
| Histologyd | |||||
| Small cell carcinoma | 8598 | 8085 (94.0) | 3991 (46.4) | 4094 (47.6) | 513 (6.0) |
| Adenocarcinoma | 28 382 | 25 043 (88.2) | 9434 (33.2) | 15 609 (55.0) | 3339 (11.8) |
| Squamous cell carcinoma | 19 466 | 18 199 (93.5) | 7730 (39.7) | 10 469 (53.8) | 1267 (6.5) |
| Other | 11 512 | 10 091 (87.7) | 4350 (37.8) | 5741 (49.9) | 1421 (12.3) |
National Program of Cancer Registries comparative effectiveness research program.3
Includes malignant tumors only. Excluded autopsy-only and nonmicroscopically confirmed cases.
Race and ethnicity were categorized as non-Hispanic White (White), non-Hispanic Black (Black), non-Hispanic Asian/Pacific Islander, non-Hispanic American Indian/Alaska Native, and Hispanic. Hispanic patients could be from any race.
Histology was grouped by International Classification of Diseases, Third Revision (ICD-3) code into small cell carcinoma (8041-8045), adenocarcinoma (8140-8239, 8250-8384, 8440-8490, 8550-8551, 8570-8574, and 8576), squamous cell carcinoma (8050-8084), and other.
Table 2. Cigarette Use Prevalence Ratios for Women Compared With Men With Lung and Bronchus Cancer From 2011 to 2016a.
| Characteristics of patients with lung cancerb | Cigarette smoking status, PR (95% CI) | |||
|---|---|---|---|---|
| Ever | Current | Former | Never | |
| Total | 0.93 (0.92-0.94) | 0.96 (0.94-0.97) | 0.92 (0.90-0.93) | 1.63 (1.58-1.68) |
| Diagnosis age, y | ||||
| 20-49 | 0.89 (0.83-0.95) | 0.91 (0.84-0.99) | 0.85 (0.75-0.95) | 1.49 (1.32-1.71) |
| 50-64 | 0.95 (0.93-0.97) | 0.90 (0.87-0.92) | 1.03 (1.00-1.07) | 1.55 (1.46-1.65) |
| 65-79 | 0.95 (0.93-0.96) | 0.99 (0.97-1.02) | 0.92 (0.90-0.94) | 1.56 (1.49-1.64) |
| ≥80 | 0.87 (0.85-0.90) | 1.12 (1.05-1.20) | 0.83 (0.80-0.85) | 1.86 (1.74-1.98) |
| Race/ethnicityc | ||||
| White | 0.95 (0.94-0.96) | 0.99 (0.97-1.01) | 0.93 (0.91-0.94) | 1.49 (1.44-1.55) |
| Black | 0.89 (0.85-0.92) | 0.84 (0.80-0.88) | 0.94 (0.89-0.99) | 2.21 (2.01-2.42) |
| Asian/Pacific Islander | 0.55 (0.47-0.64) | 0.54 (0.42-0.69) | 0.55 (0.45-0.67) | 2.61 (2.14-3.19) |
| American Indian/Alaska Native | 0.93 (0.78-1.11) | 1.06 (0.84-1.34) | 0.79 (0.61-1.04) | 2.71 (1.34-5.49) |
| Hispanic | 0.80 (0.76-0.84) | 0.86 (0.80-0.93) | 0.77 (0.72-0.81) | 2.04 (1.87-2.22) |
| Histologyd | ||||
| Small cell carcinoma | 1.00 (0.97-1.03) | 1.10 (1.05-1.15) | 0.90 (0.86-0.94) | 1.02 (0.90-1.15) |
| Adenocarcinoma | 0.91 (0.90-0.93) | 0.91 (0.89-0.94) | 0.91 (0.89-0.93) | 1.66 (1.60-1.74) |
| Squamous cell carcinoma | 0.99 (0.96-1.01) | 1.02 (0.98-1.05) | 0.97 (0.94-1.00) | 1.18 (1.08-1.28) |
| Other | 0.89 (0.86-0.92) | 0.89 (0.85-0.93) | 0.89 (0.85-0.92) | 1.78 (1.67-1.91) |
Abbreviation: PR, prevalence ratio.
National Program of Cancer Registries comparative effectiveness research program.3
Malignant tumors only. Excluded autopsy-only and nonmicroscopically confirmed cases.
Race and ethnicity were categorized as non-Hispanic White (White), non-Hispanic Black (Black), non-Hispanic Asian/Pacific Islander, non-Hispanic American Indian/Alaska Native, and Hispanic. Hispanic patients could be from any race.
Histology was grouped by International Classification of Diseases, Third Revision (ICD-3) code into small cell carcinoma (8041-8045), adenocarcinoma (8140-8239, 8250-8384, 8440-8490, 8550-8551, 8570-8574, and 8576), squamous cell carcinoma (8050-8084), and other.
The proportion of current smoking among patients aged 20 to 64 years with lung cancer was 49.8% (1094/2198) for women age 20 to 49 years and 50.8% (8983/17 673) for women age 50 to 64 years and 54.8% (1139/2077) to 56.6% (11 204/19 809) for men age 20 to 49 years and 50 to 64 years, respectively. Among patients aged 65 to 79 years, 33.1% (10 347/31 249) of women and 33.3% (11 630/34 878) of men were current smokers and 86.2% (26 986/31 294) of women and 91.2% (31 798/34 878) of men were ever smokers. For all ages combined, the proportions of current smokers were higher for Black than White or Hispanic patients.
Discussion
More than 84% of women and 90% of men with a new diagnosis of lung cancer had ever smoked, with about half of patients aged 20 to 64 years being current smokers. A higher proportion of never smokers occurred among women with lung cancer compared with men across all age groups, race/ethnicities, and most histologies. Patients with adenocarcinoma had a higher proportion of never smoking, which was consistent with past literature.5
While generalizability may be limited because of a non-national sample, our results are based on large, population-based, and geographically diverse data and may be more generalizable than those from smaller and local hospital-based data sets. Our findings reinforce the need to strengthen and increase cigarette cessation and lung cancer screening uptake among high-risk current and former smokers. Research focusing on never smokers may inform the assessment of lung cancer risk factors, such as secondhand smoke exposure, occupational exposures, radon, air pollution, and genetic factors.6
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