Comparison of extramedullary plasmacytomas with solitary and multiple plasma cell tumors of bone.

Patients with solitary osseous plasmacytomas (SOP) differ from those with extramedullary plasmacytomas (EMP) in that they are younger and the proportion of males is smaller. The median survival of the two groups is similar: 86.4 mo for SOP, and 100.8 mo for EMP. Progression-free survival, however, is much better for EMP. Only five EMP patients have progressed following initial radiation therapy: one developed a single bony lesion, two progressed to multiple myeloma, and two developed multiple EMP. Thus, 71% of EMP patients are progression free at 10 yr, and most deaths do not result from plasma cell neoplasia. In contrast, 13 SOP patients have progressed to develop additional osteolytic lesions, so that only 16% of SOP patients are progression free at 10 yr; death resulted from progression to multiple myeloma in most of these patients. In EMP patients the occurrence of involved lymph nodes at the time of diagnosis in seven, and initial relapse in regional nodes in three, suggest that consideration should be given to including regional lymph nodes in the radiation fields used to treat these patients.