Second primary malignancies after CAR T-cell therapy: A systematic review and meta-analysis of 5,517 lymphoma and myeloma patients.

CAR T-cell therapy is a potent immunotherapy for hematologic malignancies, but patients can develop long-term adverse events including second primary malignancies (SPMs) that impact morbidity and mortality. To delineate the frequency and subtypes of SPMs following CAR-T in lymphoma and myeloma, we performed a systematic review and meta-analysis. A literature search was conducted in the MEDLINE, Embase, and CENTRAL (Cochrane) databases. Following extraction of SPM cases and assignment of malignant origin, we analyzed SPM point estimates using random effect models. We identified 326 SPMs across 5,517 patients from 18 clinical trials (CT) and 7 real-world studies (RWS). With a median follow-up of 21.7 months, the overall SPM point estimate was 5.8% (95%CI 4.7-7.2). SPM estimates were associated with treatment setting (CT>RWS), duration of follow-up, and number of prior treatment lines, which were each confirmed as independent study-level risk factors of SPM in a meta-regression model. A subgroup meta-analysis of the four trials that randomized CAR-T versus standard-of-care revealed a similar risk of SPM with either treatment strategy (p=0.92). In a distribution analysis of SPM subtypes, hematologic malignancies were the most common (37%), followed by solid tumors (27%) and non-melanoma skin cancers (16%). T-cell malignancies represented a small minority of events (1.5%). We noted disease- and product-specific variations in SPM distribution. These data raise awareness of SPM as a clinically relevant long-term adverse event in patients receiving CAR T-cell therapy. However, our findings do not indicate that SPM frequency is higher with CAR-T versus previous standard-of-care strategies.