Second Primary Malignancies in Diffuse Large B-cell Lymphoma Survivors with 40 Years of Follow Up: Influence of Chemotherapy and Radiation Therapy.

Purpose: Previous studies have shown an increased risk of second primary malignancies (SPMs) in survivors of diffuse large B-cell lymphoma (DLBCL). Survivors live longer due to the intensification of and improvements in therapy; thus, we aimed to characterize SPM patterns in patients with DLBCL by treatment modality. Methods and Materials: Standardized incidence ratio and absolute excess risk of SPMs were assessed in patients with primary DLBCL from 1975 to 2016 in the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. A subgroup analyses based on, sex, race, age at the time of diagnosis, latency, and treatment modality were performed. Propensity score-adjusted cumulative incidence curves were generated, stratified by treatment and accounting for death as a competing risk. Results: In total, 45,946 patients with DLBCL were identified with a mean follow up of 70 months. Overall, 9.2% of patients developed an SPM with a standardized incidence ratio of 1.23 (95% confidence interval, 1.20-1.27). There was no difference in SPM risk between men and women or Black and White patients. Patients age <25 years were particularly susceptible to the development of SPMs, with a risk 2.5 times greater than patients aged 50 to 74 years. Temporal patterns showed increasing risk of solid malignancies and decreasing risk of hematologic malignancies over time, with bladder cancer posing the greatest absolute excess risk of any cancer type after 15 years. Patients treated with radiation therapy (RT), chemotherapy (CT), and chemoradiation therapy (CRT) all had an increased risk of SPM development compared with the general population. The cumulative incidence of SPMs was the lowest in patients treated with RT and the highest when treated with CRT. In the modern treatment era, the cumulative incidence of SPM for patients treated with CT versus CRT was not significantly different. Conclusions: In this large population-based study, we demonstrate unique SPM risk patterns based on age, latency, and treatment modality that have important implications for the treatment and screening of patients diagnosed with DLBCL.