Trends in the risk of second primary malignances after non-Hodgkin's lymphoma

Patients with non-Hodgkin's lymphoma (NHL) have an increased risk of developing second primary malignances (SPMs). In the current study, we aimed to evaluate the trends and relative clinical variables of SPM risk among NHL survivors over the past four decades. Standardized incidence ratio (SIR) and cumulative incidence frequency (CIF) were assessed in patients diagnosed with first primary NHL between 1975-2016 from the Surveillance, Epidemiology, and End Results (SEER) database. As a result, the overall SIR was 1.13 for SPMs of all sites among NHL survivors. Risk factors included male patients, "other" races, chemotherapy and radiation, and younger age at the time of NHL diagnosis. The relative and cumulative risk for both hematological and solid second cancers after NHL increased over time, whereas the increasing trend was more remarkable for hematological malignances compared with solid tumors. For individual cancer sites, the trends of SIRs varied. A significantly increasing trend of SPM risk was observed in the group receiving chemotherapy and those younger than 40 years at the time of NHL diagnosis. Recent calendar years was not an independent risk factor after adjusting age, race, gender, and therapies in the multivariate Cox proportional hazard regression. To conclude, the current study showed that the relative and cumulative risk of developing SPMs significantly increased in patients diagnosed with NHL in recent years. The trend of SPM risk was associated with certain clinical and demographic variables, and might vary according to different cancer types.