Second Primary Malignancy Risk in Patients with Multiple Myeloma Receiving CAR T-cell Therapy or Other Systemic...

This study aims to compare the risk of second primary malignancy (SPM) between patients with multiple myeloma who received chimeric antigen receptor T-cell (CAR T) therapy versus other systemic anticancer therapies (SACT).

Adult patients with multiple myeloma who initiated CAR T therapy or other SACT were identified from Komodo Health claims data and weighted to balance baseline characteristics. Cumulative incidence of SPM was estimated over 24 months, and P values were calculated for the difference between 0 and 24 months.

The study included 435 patients who received CAR T therapy and 12,268 patients who received other SACT (median follow-up, 11.8 months). Compared with other SACT, CAR T therapy was associated with similar risks of any SPM (at 24 months, 24.1% vs. 22.3%; P0-24 months = 0.31) and solid SPM (9.1% vs. 11.5%, P0-24 months = 0.32) but significantly higher risk of hematologic SPM (17.9% vs. 13.1%, P0-24 months = 0.04). In a sensitivity analysis requiring ≥ 2 claims to identify an SPM, difference in hematologic SPM risk was attenuated (5.5% vs. 4.9%, P0-24 months = 0.08). Notably, bone marrow examinations were more common after CAR T therapy (e.g., 47% vs. 13% at 0-3 months).

In this real-world dataset with relatively short follow-up, patients with multiple myeloma seemed to have a higher risk of hematologic SPM after CAR T therapy compared with other SACT. However, misclassification and detection bias cannot be ruled out. The association warrants further evaluation. Physicians should be vigilant for myeloid malignancies after CAR T therapy.