Risk of Primary Lung Cancer in Women With Personal History of Breast Cancer and Subsequent Treatment Modality in an...

Breast cancer is the most common malignant neoplasm in US women, and survivors face increased risk for subsequent malignant neoplasms, including lung cancer. Prior studies have reported associations between breast cancer treatments and lung cancer, butll contemporary data remain limited. This study evaluated lung cancer risk after breast cancer, stratified by treatment modality, in an integrated health system.

A retrospective cohort study of women diagnosed with breast cancer from 2010 to 2021 was conducted within Kaiser Permanente Northern California. Exclusion criteria included prior or early postdiagnosis lung cancer, early death, and lack of health plan membership. The primary outcome was subsequent primary lung cancer. Cumulative incidence was estimated by competing risk methods, with death as a competing event. Associations with breast cancer treatments were evaluated with Fine-Gray regression.

Of 42,290 women observed for a median of 4.6 years, lung cancer developed in 324 (0.8%). The 5-year cumulative incidence was 0.66%, with the highest incidence in current smokers (2.9%) and women aged 65 to 74 years and ≥75 years (1.1% and 1.2%, respectively). After adjustment for demographic, clinical, and tumor-related factors, breast cancer treatment exposures were not associated with lung cancer. Hispanic women demonstrated a significantly lower hazard of lung cancer compared with White women (hazard ratio, 0.54; 95% CI, 0.33-0.88).

Lung cancer risk of breast cancer survivors has increased over time. However, risk was driven by patient-level factors rather than by breast cancer treatment exposures.