Background: Patients with multiple myeloma (MM) typically relapse or become refractory (RR) to multiple lines/classes of treatment over the course of their disease. Patients treated with the three major classes of therapies (proteasome inhibitors [PI], immunomodulatory drugs [IMiD], anti-CD38 monoclonal antibodies) are considered triple-class exposed (TCE) have limited treatment options and poor prognosis once they become RRMM. This study describes the real-world characteristics and treatment patterns of Medicare beneficiaries with TCE RRMM.

Methods: Retrospective cohort study using CMS-sourced 100% Medicare Fee-for-Service claims data 1/1/15-12/31/19. Patient inclusion criteria: ≥1 MM diagnosis 1/1/16-6/30/19, ≥ age 65 at diagnosis, evidence of triple-class exposure, continuously enrolled ≥12 months pre-index and ≥6 months of post-index (or death). Treatment patterns, including duration of therapy (DOT) were measured from initiation of each new regimen following triple-class exposure (e.g., TCE1, TCE2, TCE3) until initiation of subsequent regimen, gap in treatment ≥60 days, or end of follow up. The most frequently occurring TCE1 regimens were described.

Results: A total of 2,980 Medicare beneficiaries were TCE, of which 1,672 initiated TCE1, 297 initiated TCE2, and <11 were TCE3+. Mean (SD) age at TCE1 initiation: 75.6 (5.2) years (age decreased with TCE2 and TCE3). Mean (SD) DOT and total follow up days by regimen: TCE1: 161.7 (171.6) and 354.2 (331.4), respectively; TCE2: 133.2 (150.7) days and 244.6 (216.5) days, respectively. Most commonly prescribed TCE1 regimens included: daratumumab+pomalidomide: 17.5%; carfilizomib monotherapy: 8.2%; daratumumab monotherapy: 7.2%; daratumumab+lenalidomide: 7.0%; pomalidomide monotherapy: 6.2%.

Conclusion: Treatment options for Medicare beneficiaries with TCE RRMM are limited. Prior treatment regimens were often recycled quickly, and few patients advanced to TCE2 or TCE3. Drug/drug-class combinations were highly variable (with 97 unique drug combinations observed in TCE1), indicating no clear standard of care. Further research is needed to understand treatment selection for older patients with TCE RRMM.