In a study reported in a research letter in JAMA Oncology, Jemal et al found that rates of lung cancer declined more in men vs women in the United States in recent years, such that incidence is now higher in women vs men aged ≤ 55 years.
As stated by the investigators, “A previous study from the American Cancer Society reported higher lung cancer incidence in women than men younger than 50 years in the United States, a reversal in the historically higher burden in men that was not fully explained by smoking differences…. Herein, we extended the previous analysis with an additional 5 years of data to monitor shifts in lung cancer incidence by age and sex.”
The cross-sectional study involved data on persons with lung cancer diagnosed between 2000 and 2019 from 22 registries of the Surveillance, Epidemiology, and End Results (SEER) program, representing almost 50% of the U.S. population. Cases were stratified by sex, age in 5-year increments (30–34 to ≥ 85 years), and year of diagnosis (2000–2004, 2005–2009, 2010–2014, and 2015–2019).
Declines in lung cancer incidence rates between 2000 to 2004 and 2015 to 2019 were greater in men vs women, leading to a higher incidence in women vs men aged 35 to 54 years. For example, among men aged 50 to 54 years, the rate per 100,000 person-years decreased by 44%, from 65.6 (95% confidence interval [CI] = 64.5–66.6) in 2000 to 2004 to 36.8 (95% CI = 36.1–37.6) in 2015 to 2019. Among women aged 50 to 54 years, the rate per 100,000 person-years decreased by 20%, from 48.1 (95% CI = 47.2–49.0) in 2000 to 2004 to 38.5 (95% CI = 37.8–39.3). Accordingly, the female-to-male incidence rate ratio increased from 0.73 (95% CI = 0.72–0.75) in 2000 to 2004 to 1.05 (95% CI = 1.02–1.08) in 2015 to 2019.
Among individuals aged ≥ 55 years, incidence rates continued to be lower among women vs men, with decreases in differences being observed. For example, among individuals aged 70 to 74 years, the female-to-male incidence rate ratio increased from 0.62 (95% CI = 0.61–0.63) in 2000 to 2004 to 0.81 (95% CI = 0.80–0.82) in 2015 to 2019.
The investigators stated, “Based on high-quality population-based data, we found that the higher lung cancer incidence in women than in men has not only continued in individuals younger than 50 years but also now extends to middle-aged adults as younger women with a high risk of the disease enter older age. Reasons for this shift are unclear because the prevalence and intensity of smoking are not higher in younger women compared with men except for a slightly elevated prevalence among those born in the 1960s…. Further research is needed to elucidate reasons for the higher lung cancer incidence in younger women.”
Ahmedin Jemal, DVM, PhD, of the American Cancer Society, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was supported by the Intramural Research Department of the American Cancer Society. For full disclosures of the study authors, visit jamanetwork.com.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.