Abstract
BACKGROUND: Breast cancer (BC) survivors may be at increased risk of developing second cancers compared to those without BC diagnosis due to shared risk factors and potential carcinogenic effects of cancer therapy. Lung cancer (LC) is the most common second primary cancer among BC survivors. This study aimed to evaluate the association between BC and the subsequent incidence of LC. METHODS: Women aged 55-74 were identified from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The risk of incident LC was compared by BC status using a multivariable Cox regression model with BC and smoking exposures incorporated as time-updated variables. RESULTS: 75,951 females from the PLCO trial were identified, with 5808 diagnosed with BC after enrollment. The unadjusted incidence rate (IR) of the second LC was significantly higher among BC survivors than non-BC participants (231 vs. 172 per 100,000 person-years). The adjusted hazard ratio (HR) for the second primary LC associated with BC diagnosis was 1.24 (95% CI: 1.03-1.49). CONCLUSIONS: BC diagnosis was an independent risk factor for the development of second primary LC. Consequently, BC survivors may derive benefits from enhanced LC screening interventions.