Evidence of low incidence of myelodysplastic syndrome (MDS) in patients exposed to bendamustine treatment for chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).

Abstract

e19008 Background: CLL/SLL is a treatable malignancy, which is responsive to therapies that include bendamustine. However, as with many alkylating agents, there is concern for the development of secondary malignancies and MDS after exposure to bendamustine. We evaluated the risk of MDS using electronic medical records from a geographically diverse cohort of cancer patients (pts). Methods: Pathologically confirmedCLL/SLL pts with any exposure to bendamustine were identified in the Flatiron Health database (FHD, Flatiron Health, New York [122016]). This is a longitudinal US-based cohort with > 1.5 million cancer pts drawn from over 250 cancer clinics. Pts with bendamustine exposure and no history of MDS or other malignancy were included. Pts were followed longitudinally to identify incident cases of secondary malignancies or MDS. Results: Of 3140 CLL/SLL pts in the analytic cohort, 1022 met inclusion criteria. Median follow-up after bendamustine exposure was 1.7 years. Overall, 8% received bendamustine monotherapy, 84% received combination therapy, and 8% received cycles of bendamustine monotherapy and combination therapy. Of the 1022 pts, 205 (20%) had prior antineoplastic exposure, a risk factor for MDS. During the follow-up period, five pts developed MDS (0.48% of the bendamustine-exposed cohort), one of whom had prior antineoplastic exposure. Conclusions: This real-world study demonstrated that pts received bendamustine overwhelmingly as combination therapy, and 20% had prior antineoplastic exposure. MDS related to alkylators and purine analogs can have a latency of > 3 years; in this study a minority (~20%) of pts had > 3 years of follow-up. Thus, longer follow-up is required to draw definitive conclusions regarding the risk. Nevertheless, the FHD provides a source of oncology data for studying long-term outcomes of cancer pts, which have historically been difficult to capture in epidemiological studies. At a median of 1.7 years after exposure, the current study identified a low risk of MDS after controlling for potential confounders.