Solitary Plasmacytoma Treated by Lenalidomide-Dexamethasone in Combination with Radiation Therapy: Clinical Outcomes.

Purpose: The study evaluates the results of the concurrent use of lenalidomide-dexamethasone with intensity modulated radiation therapy (IMRT) for solitary plasmacytoma in terms of toxicity and outcome.

Methods And Materials: Forty-six patients were treated for histologically proven solitary plasmacytoma (SP) between June 2007 and June 2018 in our Department (Curie Institute, Paris, France). All patients received IMRT. The median total dose was 40 Gy (range, 40-46). Prescription of concurrent lenalidomide-dexamethasone with radiation therapy was left to the discretion of the referring hematologist-oncologist and started the first day of radiation therapy for 4 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 with IMRT alone group (100% vs 77.1%, P = .02 and 81.7% vs 48.4%, P = .047, respectively). No major toxicity was found in either group.

Conclusions: 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.