Management and outcome of 500 multiple myeloma patients treated for first relapse outside clinical studies.

Treatment options for multiple myeloma (MM) at 1st relapse are expanding. The current study compared common 2nd line regimens administered in a real-world setting. MM patients registered in Maccabi health care services and treated with second line therapy during 2014-2020 were evaluated, analyzing factors affecting time to third line therapy (TT3T). The study included 500 MM patients, previously treated with proteasome inhibitor (PI)-based induction. Median age at second line treatment was 68.5 years (IQR: 61.6-76.4). Most patients received a triplet based induction composed of PI (n = 471, 94.2%), with (n = 71) or without IMID (n = 400), followed by second line treatment composed of lenalidomide-dexamethasone (RD) (n = 225, 45%) or lenalidomide-dexamethasone-daratumumab (RD-Dara (n = 104, 20.8%)). Multivariable analysis confirmed treatment type (RD-Dara vs. IMID) to be associated with a lower risk to progress to third line therapy; (HR = 0.5, 95% CI 0.3-0.86, p = 0.012). Within a median follow-up period of 22.5 months (intraquartile range 11.1-39.4 m), median TT3T was not reached in patients receiving RD-Dara vs. 32.4 months (95% CI 18.0-46.8 m) with IMID, 18 months (95% CI 10.4-25.6 m) with IMID-PI and 12.1 months (95% CI 5.6-18.7 m) with PI-based regimen. In contrast, PI vs. IMID-based therapy and increased body weight were associated with a higher likelihood of progression (HR = 2.56 (95% CI 1.49-4.42); HR = 1.43, (95% CI 0.96-2.14), p = 0.08). To conclude, second line therapy with RD-Dara was associated with a significantly longer TT3T compared with IMID-based regimen, longer than obtained with PI-IMID and PI-based regimens, in patients treated outside clinical studies and previously exposed to bortezomib.