Characteristics of Patients With Second Primary Lung Cancer Following Breast Cancer: A Retrospective Descriptive Study

Breast cancer (BC) is one of the most common malignancies and survivors are at an increased risk for secondary malignancy with lung cancer (LC) being the most common. In this retrospective study, we examine BC survivors who subsequently developed LC, and compared them to the general BC and LC population. In our study, we found the following associations that could be meaningful: an association between receiving radiation (RT) and LC (including a statistically significant p = 0.03 chance of ipsilateral LC after BC treatment with RT), a higher incidence and amount of smoking and LC, and high BRCA positivity (78.9%) in the few BC patients who had germline testing. Exploring this further can potentially lead to better risk stratification through modified low-dose CT chest screening protocols to catch LC development earlier and ultimately improve outcomes. We also found a higher incidence of EGFR mutations in NSCLC after BC (60.9%). This in association with past studies, which have shown that BC survivors who are subsequently diagnosed with NSCLC may have improved OS compared with primary NSCLC, suggest both improved prognosis and a different molecular profile of NSCLC, which warrants further investigation. Lastly, BC survivors who subsequently are diagnosed with NSCLC had earlier stage LC disease in our study, perhaps a result of surveillance, highlighting the importance of close monitoring of BC survivors. Background: Breast cancer (BC) is the most common noncutaneous malignancy in women and survivors are at an increased risk for secondary malignancy with lung cancer (LC) being the most common. There are few studies that have explored the clinicopathological specifics of LC in BC survivors. Methods: In this single-institution, retrospective study, we identified BC survivors who subsequently developed LC, examined their breast and LC clinical and pathological characteristics and compared them to the general BC and LC population as published in the literature. Results: In our study, we found the following associations that could be meaningful: an association between receiving radiation (RT) and LC (including a statistically significant P = .03 chance of ipsilateral LC after BC treatment with RT), a higher incidence and amount of smoking and LC, high BRCA positivity (78.9%) in the few patients who had germline testing, and a higher incidence of EGFR mutations in NSCLC after BC (60.9%) as well as an earlier stage of NSCLC disease. Conclusion: Treatments such as RT, genetic factors such as BRCA mutations, and tobacco use may increase the risk of developing LC amongst BC survivors. Exploring this further can potentially lead to better risk stratification through modified low-dose CT chest screening protocols to catch LCs earlier and ultimately improve outcomes. Past studies have shown that BC survivors who are subsequently diagnosed with NSCLC may have improved OS compared with primary NSCLC and our study showed a high incidence of EGFR mutated NSCLC, which also suggest both improved prognosis and a different molecular profile of NSCLC, which warrants further investigation. Lastly, BC survivors who subsequently are diagnosed with NSCLC had earlier stage disease in our study, perhaps a result of surveillance, highlighting the importance of close monitoring of BC survivors.