Effective pain control with very low dose palliative radiotherapy for multiple myeloma patients with painful osseous lesions

Abstract

Osteolytic lesions are present in 75% of multiple myeloma (MM) patients. Bone pain is a common presenting symptom. Prior case series analyzing palliative radiation (RT) for bone pain in MM patients suggest doses > 12 Gy (EQD2) provide similar excellent palliation. Recent advances in novel biologic agents have significantly improved the overall survival and quality of life for MM patients. We therefore hypothesized that lower-dose palliative RT (LDRT, i.e. EQD2 < 12 Gy) may offer a safe and effective alternative to higher-dose RT (HDRT) for the treatment of bone lesions in MM patients. We retrospectively identified all MM patients treated with RT for painful bone lesions, at either a tertiary care academic center or Veterans Affairs affiliate hospital, between 2013 and 2019. All patients underwent CT simulation and were treated with standard palliative fields. Patients were grouped into the LDRT cohort if the EQD2 < 12 Gy, with all others comprising the HDRT cohort. Patients were routinely seen in follow-up after the completion of RT and assessed for pain response and toxicity per clinic standards. We analyzed the rates of clinical pain response (CPR), differences in acute and late toxicity, duration of pain response, and retreatment rates between LDRT and HDRT groups. Thirty-four patients with 70 treated lesions were included. Twenty-four patients (49 lesions) were treated with HDRT and 10 patients (21 lesions) with LDRT. Median follow up was 16.8 months (IQR = 6.5-42.9 months) among those still alive and 94% of patients went on to receive systemic therapy. Fifty percent of patients in the HDRT cohort had rISS stage 1 MM versus 20% in the LDRT cohort. The median dose of HDRT treatment was 20 Gy (range 8-30 Gy, EQD2 12-32.5 Gy) versus 4 Gy in the LDRT group (range = 4-8 Gy, EQD2 4.67-9.3 Gy). The overall CPR rate was 97%, with CPR for HDRT = 98% and LDRT = 95%. Although acute toxicity appeared greater for the HDRT cohort (24.5%) than the LDRT cohort (9.5%), this was not significant (Χ2 p = 0.15). Five lesions required retreatment, 2 (9.5%) in the LDRT cohort and 3 (6.3%) in the HDRT cohort. Of the LDRT patients, one had progression of a pre-existing pathologic fracture and the other had subsequent CPR upon reirradiation. Pain recurred in 10% of lesions (12% HDRT versus 9.5% LDRT). The median pain response durations were not yet reached and there was no significant difference between the LDRT versus HDRT cohorts (log rank p = 0.91). This analysis suggests that LDRT effectively palliates painful MM bony lesions with acceptable CPR and duration of palliation, despite differences in patient MM stage between groups. LDRT palliation could permit patients to proceed quickly to systemic therapy by minimizing treatment duration and acute side effects. These data support further prospective comparisons of LDRT versus HDRT for palliation of MM bony lesions.