Presenting features of monoclonal gammopathies: an analysis of 684 newly diagnosed cases

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Abstract
The clinical, laboratory and radiologic features at diagnosis of 684 newly diagnosed patients with monoclonal gammopathy were revised in order to underline the differences between monoclonal gammopathies of undetermined significance (MGUS) and stage I multiple myeloma (MM). Patients were screened for inclusion in a prospective controlled protocol for treatment of MM. Those having serum or urine monoclonal component (MC) were diagnosed as MM when they demonstrated osteolysis and/or bone marrow plasma cells (BMPC) > 20%; patients not fulfilling these criteria were considered MGUS. Patients were recruited from 24 general or university hospitals from the departments of internal medicine, haematology and medical oncology. Seven-hundred-and-fifty were enrolled between January 1986 and March 1990; 684 (343 MGUS and 341 MM) were able to be evaluated for this study and 78 were stage I MM. Complete clinical, radiologic and laboratory work-up was carried out at the referral centres. The main outcome expected was the confirmation that BMPC > 20% could reliably differentiate stage I MM from MGUS. At a median follow-up of 36 months (minimum follow-up: 18 months), MGUS had a lower progression rate to overt MM, longer overall survival and different causes of death than stage I MM. Further differences concerned erythrocyte sedimentation rate (28 vs. 47, P < 0.001), per cent reduction of normal immunoglobulin (86 vs. 60%, P < 0.001), serum MC (1.6 vs. 2.2 g dl-1, P < 0.001) and thymidine kinase level (3.3 vs. 4.5 mU ml-1, P < 0.05). The study suggests that 20% BMPC can be taken as a safe cut-off point at which to differentiate MGUS from early MM and outlines a few simple parameters which can be of diagnostic aid.