Assessing Lung Cancer Rates in Non-Smokers

This is the first time lung cancer incidence rates for never smokers have been estimated based on U.S. registry data.

To our knowledge, this is the first time lung cancer incidence rates for never smokers are estimated based on U.S. registry data. Using Florida data, we found that the overall rates by racial-ethnic group are not too far apart, but Asians and Blacks have higher rates of lung cancer in never smokers (LCNS). When ranked with other cancers, in terms of incidence and mortality, LCNS is the 11th most common cancer in men and the 8th in women. Other interesting findings include:

1. Higher rates of LCNS among young women and older men;
2. LCNS is responsible for more deaths than leukemias or lymphomas among women.
3. LCNS is the second cause of cancer death among Asian American women.
4. LCNS trends are stable, while trends for lung cancer in smokers are decreasing.

Objectives

Epidemiological patterns for lung cancer among never smokers (LCNS) are largely unknown, even though LCNS cases comprise 15% of lung cancers. Past studies were based on epidemiologic or health system cohorts, and not fully representative of the underlying population. The objective was to analyze rates (and trends) of LCNS by sex, age group, and race and ethnicity based on all-inclusive truly population-based sources.

Materials and methods

Individual-level data from 2014 to 2018 on smoking status among microscopically-confirmed lung cancer cases from Florida’s cancer registry were combined with population denominators adjusted with NHIS data on smoking prevalence to compute population-based LCNS incidence rates and rate ratios. Incidence rates and proportional mortality were ranked against other cancers. Joinpoint regression analyses examined trends.

Results

Proportions of LCNS ranged from 9% among White men to 83% among Chinese women. Overall, LCNS was 13% (IRR 1.13, 95%CI 1.08–1.17) more common among men than women, but variation occurred by age group, with female rates exceeding male in younger ages. Age-adjusted rates per 100,000 were highest among Asian/Pacific Islander (API) men and women (15.3 and 13.5, respectively) and Black populations (14.6, 12.9), intermediate for White (13.2, 11.8) and lowest among the Hispanic population (12.1, 10.6). Among API women, LCNS was the second leading cause of cancer death, surpassed only by breast cancer. LCNS trends were stable over time.

Conclusion

LCNS is the 11th most frequently occurring cancer in men and 8th in women. LCNS differences by race/ethnicity are small, within a 15% range of the White population’s rates. Surprisingly, API men and women have the highest LCNS rates and proportional mortality. As smoking prevalence decreases in the U.S., LCNS cases will inevitably increase, warranting inquiry into risk factors across the lifespan.