Extramedullary plasmacytoma in the presence of multiple myeloma: clinical correlates and prognostic relevance

OBJECTIVE: We studied the clinical and laboratory features and outcomes of multiple myeloma (MM) with extramedullary plasmocytoma (EP) disease both at diagnosis and during the course of MM. PATIENTS AND METHODS: Forty-two patients of 467 patients with MM were retrospectively analyzed from both the 100th Hospital of the People’s Liberation Army and Shanghai Changzheng Hospitals. The clinical characteristics, laboratory parameters, responses, risk factors, and outcomes were analyzed. RESULTS: The median age was 53 years with a male/female sex ratio of 34:8. Twenty-six patients had EP disease at the time of diagnosis, and 16 patients developed EP during the course of the disease. We found that the Durie–Salmon stage, serum lactate dehydrogenase level, beta-2-microglobulin, complete blood counts, albumin, and the type of immunoglobulin (Ig) were not associated with the development of EP disease. Patients who developed EP during the course of MM had a higher ratio of plasmocytes and premature plasmocytes in the bone marrow with lower C-reactive protein level and earlier stage of International Staging System for Lung Cancer at the diagnosis of MM compared with patients who presented with EP at diagnosis. Once the patients developed EP disease, they frequently showed resistance to chemotherapy. With a median follow-up of 30 months, 19 patients were alive. Log-rank univariate analysis showed that patients with EP who had normal C-reactive protein, higher hemoglobin, lower serum lactate dehydrogenase, and stage I of International Staging System for Lung Cancer had longer survival. However, cyclooxygenase multivariate analysis failed to show statistical significance for any factor. CONCLUSIONS: EP disease is the MM end-phase and is not a rare manifestation of MM with a cumulative incidence of 9% of MM. The prognosis is very poor once the diagnosis of EP disease is concurrent with MM.