Low Vs High Dose Carfilzomib (Cfz) With Dexamethasone (Dex) For Relapsed/Refractory Multiple Myeloma (Rrmm): Results Of Swog S1304.

8015Background: Cfz has u003e 1 FDA approved doses in RRMM. Dose-response correlation is assumed without prospective data to compare efficacy of low-dose (27 mg/m2; LDC) vs high-dose Cfz (56 mg/m2; HDC). Methods: S1304 (NCT01903811), a randomized phase 2 trial compared LDC + dex vs HDC + dex, in Cfz na•ve RRMM pts with ²6 prior lines of treatment (Tt). Cycle 1 was 20 mg/m2 with total planned Tt 1 year on each arm. Those progressing on LDC could cross to HDC. Results: 143 pts were enrolled, with 121 eligible + evaluable (LDC: 64, HDC: 57). Median follow up was 32 months (mo). There were no significant differences in pt characteristics or ORR between study arms (Table). Median PFS on HDC was 8 mo vs 6 mo on LDC (intent to treat); not statistically significant (HR 0.996 95% CI 0.785, 1.265). OS on 2 arms was also not significantly different (HR 1.069 95% CI 0.797, 1.434). PFS or OS were not significantly different between 2 arms in 1-3 vs 4-6 prior lines of Tt, bortezomib (btz) refractoriness or among pts who re...