A systematic review and meta-analysis estimated the frequency of second primary malignant neoplasms (SPMs) after T-cell engaging bispecific antibody therapy in adults with non-Hodgkin lymphoma and multiple myeloma. The analysis pooled data from 20 studies (26 cohorts; 2,551 patients) identified from PubMed and Embase through Oct. 1, 2025. Across available follow-up, the pooled estimated proportion of reported SPMs was 3.5% at a median 17.4 months, with discontinuation linked SPMs estimated at 2.2% and SPMs leading to death at 1.4%. The review reported no study-level covariate association with total SPM frequency in exploratory meta-regression. The authors emphasize that follow-up remains relatively short and reporting heterogeneous, but the results position SPM occurrence as measurable and clinically relevant even as bispecifics shift earlier in treatment lines.