Place of modern imaging modalities for solitary plasmacytoma: toward improved primary staging and treatment monitoring

Radiation therapy (RT) is the mainstay of treatment of solitary plasmacytoma. In most cases, doses ranging from 40 to 50 Gy yield in a local control more than 80%. However, the prognosis of patients with SP is marked by a high rate of transformation to multiple myeloma (MM), and there is no demonstrated benefit of adjuvant chemotherapy for decreasing this probability. However, clinical benefits could be reached from improving screening for other primary sites of plasmacytoma and earlier discovering signs suggestive of MM. Since such strategy could provide significant information regarding both prognosis and therapy, it has become first importance to improve initial staging of tumor widespread. Although conventional skeletal X-ray survey remains standard, usual sensitivity of radiographies does not permit diagnosing early myeloma lesions and a significant number of patients with supposed SP might be understaged and do not receive the appropriate treatment. The development of more sensitive and specific imaging modalities will make it feasible to earlier detect subclinical lesions, thus leading lead to new approaches in the treatment strategies. Here, we discuss the benefits and limitations of magnetic resonance imaging and positron emission tomography for primary staging of patients with solitary plasmacytoma. Both imaging modalities could also improve target volume delineation and assessment of tumor response after RT.