Risk and prognosis of secondary breast cancer after radiation therapy for non-Hodgkin lymphoma: a massive population-based analysis

Purpose One of the best ways to control non-Hodgkin lymphoma (NHL) locally is radiation therapy (RT), which is a crucial component of care for many patients. There has not been any research on the risk and prognosis of secondary breast cancer (SBC) in females with NHL receiving RT. Methods In our study, females with NHL as their initial cancer diagnosis were included from 1975 to 2018 in the Surveillance, Epidemiology and End Results (SEER) database. Using Fine and Gray's competing risk regression assess the cumulative incidence of SBC. The standardized incidence ratios (SIR) and radiation-attributed risk (RR) for SBC were assessed using Poisson regression analysis. We evaluated the overall survival (OS) of SBC patients using the Kaplan-Meier technique. Results Of the 41,983 females with NHL, 10,070 received RT and 320 (3.18%) developed SBC. 31,913 females did not receive RT and 805 (2.52%) developed SBC. RT was significantly related with a greater chance of acquiring SBC in the Fine-Gray competing risk regression (adjusted hazard ratios (HR) = 1.14; 95% confidence intervals (CI), 1.09-1.30; P = 0.011). When an NHL diagnosis was made at an older age, the dynamic SIR and RR for SBC also declined over time. Regarding general survivability, there was not statistically significant (P = 0.970) after propensity score matching (PSM). Conclusions RT is an independent risk factor for SBC in females with NHL. Special attention should be paid to the monitoring of breast cancer indicators in them, especially young.