Clinical features and outcome of multiple myeloma arising from the transformation of a monoclonal gammapathy of undertermined significance

Patients with a monoclonal gammapathy of undertermined significance (MGUS) are usually submitted to a periodical clinical follow-up, but it is not kno wn if this surveillance can ameliorate the prognosis of a plasma cell malig nancy that will be eventually detected. We compared the clinical and labora tory characteristics at onset, the response to chemotherapy and the surviva l, of 21 cases of newly diagnosed multiple myeloma (MM) arising from the ma lignant transformation of MGUS and 41 cases without a previous history of M GUS, recruited to the same first-line treatments over a 3-years period. The former group showed a significant lower frequency of advanced stages as we ll as other several prognostic factors of high risk including anemia, renal failure, bone lesions and increase of beta2 microglobulin and C-reactive p rotein levels. Despite a similar response to treatment of the two groups, M M arising from MGUS showed a significantly longer median survival than MM w ithout prior MGUS. This was particularly true for stage I, while stages II and III behaved similarly. We conclude that the regular clinical monitoring of MGUS patients allowed the identification of earlier malignant transform ation, when tumor burden is lower, as indicated by lower beta2 microglobuli n levels and marrow plasmacytosis of stage IMM arising from MGUS. Moreover, a slower proliferation rate of myeloma cells, as suggested by lower C-reac tive protein levels, may be considered so as to explain the longer survival of these patients.