Overall and complete response rates as potential surrogates for overall survival in relapsed/refractory multiple myeloma.

The correlation between response and survival has not been well-studied in relapsed or refractory multiple myeloma (RRMM). A systematic literature review of Medline, Embase and Cochrane databases (2010-06/2020) and relevant congresses (2018-2020) was performed to identify randomized clinical trials in RRMM reporting median overall survival (mOS), progression-free survival and response endpoints. The relationship between mOS and response endpoints was analyzed using Pearson's product-moment correlation. A total of 81 records for 65 original studies, representing 12,827 patients were included. The correlation was moderate for mOS with overall response rate (Pearson r = 0.79), very good partial response (r = 0.73) and duration of response (r = 0.78); all were statistically significant. In linear regression models, estimated mOS gain was 0.48, 0.47 and 1.94 months per percentage point of overall response rate, very good partial response and complete response, respectively (all p < 0.001). Significance was maintained after adjustment for age, relapsed versus refractory multiple myeloma and study year. The analysis was limited by small sample sizes and inconsistent reporting of study-level covariates. These findings support short-term response-based endpoints as surrogates to survival in RRMM.