Role of Radiotherapy-Induced Malignancies in Patients with Both Breast and Lung Cancer Diagnoses

Abstract

Background:Breast and lung cancer are two of the most commonly diagnosed cancers in North America. While patients are living longer with advances in treatment and supportive care, some patients are being diagnosed with a second malignancy. The primary objective in this study was to assess the correlation between the development of an ipsilateral lung cancer or breast cancer, and prior radiation therapy. In addition, we sought to report the survival outcomes of patients in these clinical scenarios. Methods: We conducted a single institution (the Ottawa Hospital Cancer Centre) retrospective review of patients with the diagnoses of both breast and lung cancer treated between 1995 and 2013. Patients were included if they received radiation for a breast primary, and subsequently developed an ipsilateral lung primary, or vice-versa. Data included patient demographics, lifestyle factors, tumor location and subtype, cancer stages, treatment modalities, and survival outcomes. Results: Of 252 patients included in the study, 217 patients developed a breast primary first, with 35 patients developing a lung primary first. Median disease-free survival from the second primary diagnosis was 36 months in breast primary first patients, and 59 months in the lung primary first cohort. There was no significant correlation between the laterality of radiation treatment and side of second primary based on Fisher’s exact test. Conclusions: Our data reveal no association between side of radiation treatment and subsequent cancer development. The benefits of radiotherapy outweigh the risk of radiation-induced primaries. Longer term studies with matched patient cohorts are required to further assess treatment and lifestyle factors that may contribute towards the development of second malignancies.