Other primary malignancies are associated with inferior survival in multiple myeloma: a single-center matched...

Other primary malignancies (OPMs) may complicate diagnostic assessment, treatment sequencing, and prognostic evaluation in multiple myeloma (MM). This study characterized the spectrum and timing of OPMs and evaluated their association with overall survival (OS).

We retrospectively screened 461 unique patients with MM treated or followed at a single center between August 8, 2019, and June 6, 2026. Patients with OPMs were categorized as OPM-first, synchronous, or MM-first and matched 1:2 with patients without OPMs by sex, age at MM diagnosis, and year of MM diagnosis. OS was evaluated using Kaplan-Meier analysis, matched-set-stratified log-rank testing, and stratified Cox regression.

Twenty-seven patients had OPMs, corresponding to a crude proportion of 5.9%. Lung cancer (37.0%) and prostate cancer (18.5%) were the most common OPMs. Ten patients (37.0%) were classified as OPM-first, 12 (44.4%) as synchronous, and 5 (18.5%) as MM-first. OPMs affected MM management in 29.6% of patients, whereas MM or anti-myeloma treatment affected OPM management in 18.5%; treatment was modified because of documented or anticipated overlapping toxicities in 29.6%. Median OS was 46.2 months in cases and was not reached in matched controls. OPMs were associated with inferior OS in the stratified Cox analysis (hazard ratio, 3.92; 95% CI, 1.35-11.37; P = 0.012), and the association persisted after MM-first cases were excluded.

Lung and prostate cancers were the most common OPMs in this cohort, highlighting the need for heightened clinical attention to these malignancies in patients with MM. The presence of an OPM was associated with inferior OS; however, this finding should be interpreted cautiously because of the small sample size and marked tumor heterogeneity. When both malignancies require active treatment, multidisciplinary assessment is important to determine treatment priority according to disease activity, treatment urgency, and the patient's overall condition.