Abstract PO-130: Disparities in risk of second primary lung cancer among lung cancer patients in the United States
Authors: Choi Eunji , Luo Sophia J. , Aredo Jacqueline V. , Neal Joel W. , Backhus Leah M. , Wakelee Heather A. , Han Summer S. 
Published: January 2022

Introduction: Lung cancer is the leading cause of cancer death in the U.S. Despite recent survival improvements, racial and socioeconomic disparities still exist in lung cancer incidence and survival. Furthermore, recent studies showed that lung cancer survivors have a high risk of developing second primary lung cancer (SPLC). While racial and socioeconomic disparities have long been examined for lung cancer survival and incidence, little is known about their impacts on SPLC risk among lung cancer survivors. This study evaluated the disparities in SPLC incidence by calculating the standardized incidence ratio (SIR) of the observed SPLC incidence versus the expected incidence of initial primary lung cancer (IPLC) across different socioeconomic, acculturation, and smoking-related factors using county-level data obtained from the Surveillance, Epidemiology, and End Results Program (SEER). Methods: We identified 158,018 patients diagnosed with IPLC between 2000 and 2013 in SEER. SPLC was defined as a newly developed primary lung cancer after 2 years from IPLC diagnosis and was followed through 2018. The SIR was calculated as the ratio of the observed SPLC incidence versus the expected incidence of IPLC in the general population across different factors. Indicators of socioeconomic status, acculturation factors, and smoking prevalence in SEER were derived from county-level data using the American Community Survey and the Behavioral Risk Factor Surveillance System (BRFSS). The quintiles of these indicators were created using the data obtained across all 3,142 valid U.S. counties. We applied the Pearson's chi-squared test to evaluate the difference in SIRs across quintiles of the indicators we created, applying a statistical significance of α &lt; 0.005 after adjusting for multiple testing. Results: Among 158,018 IPLC patients, 10,650 (6.7%) developed SPLC over 626,853 person-years. The incidence of SPLC was 6 times higher than the IPLC incidence in the general population, with an overall SIR of 6.2 (95% Confidence Interval (CI): 6.09-6.32). Notably, the SIR, i.e., the ratio between the SPLC incidence and the IPLC incidence, was significantly higher among individuals who live in counties with the lowest quintile of median family income (&lt;$51,770) versus the highest quintile (&gt;$74,331) (SIR 7.18 versus 6.10, P&lt;1 × 10−6). Furthermore, the ratio between the SPLC versus the IPLC incidence was highest (SIR 8.01, CI: 7.36-8.71) among those who live in counties with the highest quintile of smoking prevalence (&gt;29.6%) versus SIR of 5.77 (CI: 5.63-5.91) with the lowest quintile of smoking prevalence (&lt;20.4%) (P=3.4 × 10−3). Race/ethnicity and acculturation factors, including immigration status, did not achieve statistical significance. Discussion: Significant disparities exist in SPLC incidence among lung cancer survivors who live in areas with a low median family income and high smoking prevalence. Targeted SPLC surveillance for lung cancer survivors from an underserved population would be needed to reduce the existing disparities.

Citation Format: Eunji Choi, Sophia J. Luo, Jacqueline V. Aredo, Joel W. Neal, Leah M. Backhus, Heather A. Wakelee, Summer S. Han. Disparities in risk of second primary lung cancer among lung cancer patients in the United States [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-130.