The elevation of eosinophils could prolong the time to the next treatment in patients with RRMM who are treated with lenalidomide

Abstract

Lenalidomide (LEN) directly targets myeloma cells and stimulates an immunological response. Eosinophils (Eo) have a variety of immunological functions and play roles in the development of allergic diseases and asthma. Eo level elevations have been shown to represent immunological activity in patients with myeloma who are treated with LEN. The purpose of this study was to investigate the clinical significance of Eo level elevation in patients with relapsed or refractory multiple myeloma (RRMM) who were treated with LEN. We reviewed the medical records of patients with RRMM who were treated with LEN-containing regimens at the Jikei Kashiwa Hospital, between November 2010 and June 2018. The included patients were followed-up until March 2019, and the median follow-up period was 24.4 months. Fifty-nine patients with RRMM who were treated with LEN were analyzed, and median patient age was 73 years. An elevation of Eo was defined as an increase in Eo count of 250 /microL or more during the first cycle, compared to the level on day one of the first cycle. As salvage chemotherapy, 39, 8, 4, 3, 3, and 2 patients received LEN plus dexamethasone (Rd), elotuzumab plus Rd (ERd), daratumumab plus Rd (DRd), ixazomib plus Rd, bortezomib plus Rd, and LEN, melphalan, plus prednisone, respectively. The median time from diagnosis to the start of LEN was 25.9 months. The median number of prior regimens was two. The percentage of patients with the Eo elevation was 22.0%. There were no a significant relationships among Eo elevation and age, sex, M protein type, international staging system (ISS), serum lactate dehydrogenase level, serum C-protein level, number of prior chemotherapies, prior bortezomib, dose of lenalidomide, and dose of corticosteroid. The overall response rate (ORR) in the groups with Eo level elevation and non-elevation were 84.6% and 63.0%, respectively (P = 0.189). The elevation of Eo was not related to any grade of skin rash (P = 0.713). The median time to next treatment (TTNT) of the Eo elevation group was significantly longer than that of the Eo non-elevation group (40.3 vs 8.4 months, P = 0.017). In addition, the median TTNT in the Eo elevation group with partial response (PR) or better was significantly longer that of the Eo non-elevation group with a PR or better (40.3 vs 11.9 months, P = 0.021). In the multivariate analysis, the Eo elevation was a significant good prognostic factor for TTNT (hazard ratio 0.401, P = 0.043). The overall survival was similar between the Eo elevation and non-elevation groups (P = 0.334). From our findings, we conclude that Eo level elevations are common and can prolong TTNT in patients with RRMM who are treated with LEN.