Solitary plasmacytoma: Lenalidomide-Dexamethasone combined with radiation therapy improves progression-free survival and multiple myeloma-free survival

PURPOSE: To evaluate the results of the concurrent use of lenalidomide-dexamethasone with intensity-modulated radiation therapy (IMRT) for solitary plasmacytoma in terms of toxicity and outcome Materials & Methods: Forty-six patients were treated for histologically proven SP between June 2007 and June 2018 in our Department (XXX). All patients received IMRT. The median total dose was 40 Gy (range, 40-46). Prescription of concurrent lenalidomide-dexamethasone with radiotherapy was left discretion of the referring hematologist-oncologist and started the first day of radiotherapy for four cycles.

RESULTS: Twenty-seven solitary plasmacytoma were treated with IMRT alone and 19 with lenalidomide-dexamethasone in association with IMRT. At 5 years, the local control, multiple myeloma-free survival (MMFS) and progression-free survival (PFS) rates were 96.3%, 85.4%, and 60%. MMFS and PFS were significantly higher in the IMRT plus lenalidomide-dexamethasone group compared to IMRT alone group (100% vs 77.1%, p=0.02 and 81.7% vs 48.4%, p=0.047, respectively). No major toxicity was found in either group.

CONCLUSION: Lenalidomide-dexamethasone in association with IMRT in the treatment of solitary plasmacytoma is safe and improves MMFS and PFS. Further prospective and comparative studies are needed to confirm these results.