Hyperfractionated Cyclophosphamide and Dexamethasone Alone or in Combination with Daratumumab and/or Carfilzomib for the Treatment of Relapsed or Refractory Multiple Myeloma: A Single-Center Retrospective Analysis

Background: Hyperfractionated cyclophosphamide and dexamethasone (HyperCd) alone, or with carfilzomib(K) and/or daratumumab(D), represents a potential treatment option when rapid disease control is needed for patients with aggressive presentations of relapsed/refractory multiple myeloma (RRMM). Patients and Methods: This is a single-center, retrospective analysis of adult patients with RRMM who received HyperCd with or without K and/or D between May 1, 2016 and August 1, 2019 at the University of Texas MD Anderson Cancer Center. We here report treatment response and safety outcomes. Results: Data from 97 patients, 12 with plasma cell leukemia (PCL), were reviewed in this analysis. Patients had had a median of 5 prior lines of therapy and received a median of 1 consecutive cycle of hyperCd-based therapy. The overall response rate (ORR) of all patients was 71.8% (HyperCd 75%, HyperCdK 64.3%, D-HyperCd 73.3%, and D-HyperCdK 76.9%). Median progression-free survival and overall survival among all patients was 4.3 months (HyperCd 3.1 months, HyperCdK 4.5 months, D-HyperCd 3.3 months, and D-HyperCdK 6 months) and 9.0 months (HyperCd 7.4 months, HyperCdK 9.0 months, D-HyperCd 7.5 months, and D-HyperCdK 15.2 months), respectively. Grade 3/4 hematologic toxicities were common, thrombocytopenia being the most frequent at 76%. Notably, 29-41% of patients per treatment group had existing grade 3/4 cytopenias at initiation of hyperCd-based therapy. Conclusion: HyperCd-based regimens provided rapid disease control among MM patients, even when heavily pre-treated and with few remaining treatment options. Grade 3/4 hematologic toxicities were frequent, but manageable with aggressive supportive care.