Abstract LB378: Incidence and trends in subsequent primary lung cancer by sex in the United States
Authors: Sung Hyuna , Jiang Chenxi , Bandi Priti , Schafer Elizabeth , Islami Farhad , Jemal Ahmedin 
Published: April 2024

Abstract
Importance The difference in lung cancer incidence by sex has been extensively documented in the US. Nonetheless, previous studies did not differentiate between first primary lung cancers (FPLCs) and those that occur in individuals with a history of cancer (i.e., subsequent primary lung cancers or SPLCs).
Objective To examine whether the sex-specific pattern in lung cancer incidence rates differ by tumor sequence in the US.
Design, Setting, and Participants Lung and bronchus (hereafter, lung) cancer diagnosed from 2001-2020 at ages 20 or older, stratified by sex and tumor sequence (first versus subsequent), were identified from the U.S Cancer Statistics Public Use Database.
Main Outcome and Measures Age-standardized (2000 US standard population) incidence rates and female-to-male incidence rate ratio (IRRs) were calculated using SEER*Stat, overall and by age groups (20-49, 50-59, 60-69, 70+ years). Trends in incidence rates were quantified using Joinpoint program, estimating annual percent change (APC).
Results From 2001-2020, there were 3,333,495 FPLC diagnoses and 961,130 SPLC diagnoses. For FPLC, the incidence rate in women was 28% lower than in men (57.7 versus 79.8 per 100,000; IRR=0.72, 95%CI=0.72-0.72) with the sex gap greater with increasing age from 0.96 (95%CI=0.95-0.97) in individuals aged 20-49 years to 0.69 (95%CI=0.69-0.70) in those aged 70 years or older. For SPLC, the incidence rate in women was 33% lower than in men (17 versus 25 per 100,000; IRR=0.67, 95%CI=0.67-0.68). However, the lower incidence of SPLC in women was seen only among people aged 60 or older. Intriguingly, the incidence rate of SPLC in women was twice as high as in men among those aged 20-49 years (0.83 versus 0.44 per 100,000; IRR=1.90, 95%CI=1.83-1.96) and 25% higher among those aged 50-59 years (11.05 versus 8.84 per 100,000; IRR=1.25, 95%CI=1.23-1.27). From 2001-2019, incidence rates of FPLC decreased for both men (1.88% to 3.45% per year) and women (1.23% to 2.24% per year), although the decrease began in 2006 in women. For SPLC, the incidence rate in men showed a 2.74% annual increase from 2001-2007, followed by a decrease (APC=-1.91%, 95%CI=-2.27 to -1.68) from 2012-2019, while the incidence rate in women exhibited a 4.05% annual increase from 2001-2009, followed by a continued increase at a slower pace (APC=0.48%, 95%CI=0.28-0.69). The rising trends in SPLC among women were primarily driven by those aged 50 or older. In particular, the incidence rate of SPLC among women aged 70 or older increased by 5.4% per year from 2001-2009, followed by a 0.92% annual increase from 2009-2019.
Conclusion Sex-specific patterns in lung cancer incidence differ considerably between first versus subsequent primary lung cancer. The findings highlight variations in sex-specific exposures within different populations at risk such as the general population versus cancer survivors. Further research is needed to identify reasons for the female predominance of SPLC among young adults and the concerning rise of SPLC rates in women.
Citation Format: Hyuna Sung, Chenxi Jiang, Priti Bandi, Elizabeth Schafer, Farhad Islami, Ahmedin Jemal. Incidence and trends in subsequent primary lung cancer by sex in the United States [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB378.