Purpose: To analyze the outcomes of patients treated for solitary plasmacytoma with definitive radiotherapy (RT).
Material and Methods: Thirty-two patients with solitary plasmacytoma of bone (SPB; 22 patients) and extramedullary plasmacytoma (EMP; 10 patients) were treated between 1963 and 2006. The median RT dose was around 42.7 Gy (range, 15–54 Gy) over a median of 25 fractions (range, 1–32 fractions). No patient received adjuvant chemotherapy. Median follow-up was 10.1 years (range, 1–33 years). Median follow-up on living patients was 7.3 years (range, 2.1–33 years).
Results: The 10-year local-control rate after RT was 87%. All 4 patients who developed a local recurrence had SPBs ≥5 cm. The 10-year multiple myeloma-free survival rates were: SPB, 30%; EMP, 90%; and overall, 50%. Progression to multiple myeloma occurred at a median of 25.1 months after RT. The 10-year overall and cause-specific survival rates were 65% and 77%, respectively. The 10-year cause-specific survival rate was 65% for patients with SPB versus 100% for those with EMP (P = 0.006).
Conclusion: Moderate dose RT results in a high rate of local control. Patients with SPB are more likely to progress to multiple myeloma, which adversely affects their survival compared with those with EMP.