Lung cancer in never smokers: Distinct population-based patterns by age, sex, and race/ethnicity

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.

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.

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.

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 US, LCNS cases will inevitably increase, warranting inquiry into risk factors across the lifespan.