Brief Report LYMPHOID NEOPLASIA Outcome prediction in plasmacytoma of bone: a risk model utilizing bone marrow flow cytometry and light-chain analysis

Solitary plasmacytoma of bone (SPB) is characterized by localized areas of bone destruction by monoclonal plasma cells in the absence of clinical, laboratory, and radiologic features of multiple myeloma (MM). Local irradiation remains the treatment of choice. United Kingdom national guidelines recommend doses of 40 to 50 Gy depending on tumor size, with a 2-cm margin, because this provides excellent local control. A significant proportion of patients will however progress with new lesions outside the irradiation field or, more typically, with generalized myeloma. The overall incidence of progression is 37% to 72%, with median reported times to progression (TTP) of 2 years or less. We hypothesized that progression in SPB might occur as a result of occult disease outside of the irradiation field. To further evaluate this, we usedmultiparameter flow cytometry (MFC) to assess staging bone marrow (BM) samples for the presence of occult disease and determine its impact on outcome.