RADIOTHERAPY IN THE TREATMENT OF SOLITARY PLASMACYTOMA

`Solitary plasmacytoma of bone (SPB) and extramedullary plasmacytoma ( EMP) are rare. High local control rates are reported with radiotherapy , although the optimal dose and extent of radiotherapy portals remains controversial. Between 1983 and 1993, 30 patients with solitary plasm acytoma were seen at the Regional Cancer Centre, Trivandrum, India. 23 patients had SPB and seven EMP. The mean age was 52 years and the mal e to female ratio 3.2:1. Diagnosis of SPB was confirmed by biopsy in 1 6 patients and tumour excision in seven. 20 patients received megavolt age radiotherapy to the bone lesion with limited margins, and one rece ived chemotherapy. Two patients who underwent complete tumour excision received no further treatment. All seven patients with EMP received m egavoltage radiotherapy, four following biopsy and three after tumour excision. Local control was achieved in all patients with SPB. Nine pr ogressed to multiple myeloma and one developed a solitary plasmacytoma in another bone. Six patients with EMP achieved local control. Three later progressed to multiple myeloma and one had local relapse. Median time to relapse was 28 months in SPB and 30 months in EMP. 5-year ove rall survival rates were 82% and 57% for patients with SPB and EMP; re spectively. The corresponding progression free survival rates were 55% and 50%, respectively. Age, sex, site of tumour, serum M protein and haemoglobin levels did not significantly influence progression free su rvival. The extent of surgery, radiotherapy dose or time to relapse we re not significant prognostic factors. Radiotherapy appears to be an e ffective modality of treatment of solitary plasmacytoma. No dose-respo nse relationship is observed, and high local control rates are achieve d with limited portals. Progression to multiple myeloma is the commone st pattern of failure, although no prognostic factors for progression are identified. The role of chemotherapy in preventing disease progres sion needs further evaluation.