Solitary plasmacytoma of bone: Mayo Clinic experience.

A review of 46 cases of solitary plasmacytoma of bone was undertaken in an attempt to better define the clinical features and prognostic indicators associated with this disease. Criteria for inclusion in the study included the following: (a) solitary lytic bone lesion on skeletal survey; (b) histologic confirmation of the lesion; and (c) bone marrow plasmacytosis of less than 10 percent. Patients with extramedullary plasmacytomas and osteosclerotic lesions were excluded. All patients were evaluated with serum and urine protein studies at the time of diagnosis. The median follow-up was 90 months with a minimum of 30 months. Fifty-four percent of the lesions involved the vertebral column. The thoracic spine was the single most commonly involved site (13/46 patients). The initial lesion was treated with radiotherapy in all but three patients in whom complete surgical resection was achieved. Total doses ranged from less than 20 Gy to 70 Gy with a median of 39.75 Gy. Overall, 54% developed multiple myeloma, 2% failed with new bone lesions without multiple myeloma, and 11% developed local recurrences. No patient receiving 45 Gy or more to the solitary lesion had a local failure. While the median time to progression was 18 months, 23% of the failures occurred after 60 months. The five local failures occurred at 7, 12, 18, 40, and 114 months. The overall survival was 74% at 5 years and 45% at 10 years. The 5- and 10-year disease-free survivals, however, were 43 and 25%, respectively. Evidence of abnormal serum and/or urine protein was found in 25 of 46 patients. Neither survival nor disease-free survival was significantly influenced by the presence of abnormal proteins even if they persisted after irradiation.