(C-222) Incidence of second primary T-cell non-Hodgkin lymphoma among multiple myeloma patients: evidence from real-world data

Background: Multiple myeloma (MM) patients have a higher risk of second primary hematological malignancies than general population. T-cell non-Hodgkin lymphoma (NHL) accounts for 10-15% of NHL, however incidence of T-cell NHL among MM patients is under-studied.

Objectives: To estimate incidence of T-cell NHL among MM patients in the US.

Methods: A retrospective cohort study was conducted using real-world data to estimate incidence of T-cell NHL among MM patients in the US. Data from 6 claims and 2 electronic health records databases, which covered patients’ information from 2015 to 2024, were used. Five cohorts were generated as follows: incident MM patients regardless of treatment received later, new users of immunomodulatory drug (IMiD), proteasome inhibitor (PI), or anti-CD38 monoclonal antibody (mAb), and triple-class exposed (TCE) MM patients. The outcome was defined as 1) the earliest recorded diagnosis code of T-cell NHL or 2) the earliest recorded diagnosis code of skin neoplasms of uncertain behavior followed by a more specific T-cell NHL code within 60 days, whichever was dated earlier. Patients were followed from the index to T-cell NHL diagnosis, death, or end of data, whichever occurred first. The index of incident MM patients was date of the first diagnosis of MM. For cohort of new IMiD, PI, or anti-CD38 mAb users, the index date was the date of the first observed use of the drug. For TCE MM, the index was the date when patients started a new treatment after completion of a PI, IMiD, and anti-CD38 mAb. In the analysis, incidence proportion and incidence rate were estimated.

Results: Among all incident MM patients (median follow-up: 2.1 years [Y]), the incidence proportion of T-cell NHL ranged from 0.17% to 0.35%. The incidence rate of T-cell NHL ranged from 0.06 to 0.16 per 100 person years (PY). Among new users of IMiD (median follow-up: 2.2 Y), the incidence proportion ranged from 0.12% to 0.18%, and the incidence rate ranged from 0.04 to 0.08 per 100 PY. Among new users of PI (median follow-up: 2.1 Y), the incidence proportion ranged from 0.12% to 0.34%, and the incidence rate ranged from 0.05 to 0.16 per 100 PY. Among new users of anti-CD38 mAb (median follow-up: 1.6 Y), the incidence proportion ranged from 0.07% to 0.18%, and the incidence rate ranged from 0.04 to 0.11 per 100 PY. For TCE MM cohort (median follow-up: 1.5 Y), only two databases provided sufficient sample size to estimate incidence proportion (0.13% to 0.31%) and incidence rate (0.10 to 0.22 per 100 PY).

Conclusions: Our analysis suggests that incidence proportion of second primary T-cell NHL among MM patients is lower than 0.5%. The estimated incidence may not be generalizable to other regions due to heterogeneity in diagnostic guidelines, insurance coverage, and administrative coding practices.