The Safety and Efficacy of Radiation Therapy with Concurrent Dexamethasone, Cyclophosphamide, Etoposide, and Cisplatin-Based Systemic Therapy for Multiple Myeloma

The concurrent delivery of radiation therapy (RT) with salvage chemotherapies in the management of relapsed and refractory multiple myeloma (MM) is an area of ongoing investigation. This study examined the safety and efficacy of palliative RT given in the setting of concurrent dexamethasone, cyclophosphamide, etoposide, and cisplatin (DCEP). Fifty-five patients with MM received RT to 64 different sites within three weeks of receiving DCEP from 2010 to 2020. A median dose of 20 Gray (range 8-32.5 Gy) was delivered in a median of 5 fractions (range 1-15). Patients received a median of 1 cycle (range 1-5) of DCEP. Rates of hematologic and RT toxicity were recorded along with pain, radiographic, and laboratory responses to treatment. RT was completed in 98% of patients. 21% of patients experienced RTOG grade 3+ hematologic toxicity before RT, which increased to 35% one-month post-RT (P = .13) before decreasing to 12% at 3 to 6 months (P = .02). The most common toxicity experienced was thrombocytopenia. Grade 1 to 2 non-hematologic RT-related toxicity was reported in 15% of patients while on treatment and fell to 6% one-month after completing RT. Pain resolved in 94% of patients with symptomatic lesions at baseline. Stable disease or better was observed in 34/39 (87%) of the targeted lesions on surveillance imaging. RT administered concurrently with DCEP was well-tolerated by most of the patients in this series, with low rates of hematologic and RT-related toxicity. RT was also very effective, with the vast majority of patients demonstrating resolution of their pain and a significant response on follow-up imaging. Little is known about the safety and efficacy of delivering radiation therapy (RT) with concurrent DCEP (dexamethasone, cyclophosphamide, etoposide, and cisplatin) chemotherapy in patients with multiple myeloma. In this study, DCEP plus RT was safe, with low rates of grade 3+ hematologic toxicity and grade 2+ RT-related events. It was also effective at alleviating pain at symptomatic sites of disease and producing a radiographic response on imaging.