Rate of M-component changes and plasma cell labeling index in 25 patients with multiple myeloma treated with peptichemio.

Twenty-five consecutive patients with previously untreated multiple myeloma were studied for bone marrow plasma cell labeling index, response to peptichemio induction therapy, and rate of M-component (MC) changes during the course of the disease. They received intermittent melphalan or cyclophosphamide as maintenance therapy and peptichemio associated with vincristine at first relapse. The response rate (76%) was independent of clinical stage, evaluated according to Merlini et al and to Durie and Salmon. Among responsive patients, rapid responders (half-life of MC decrease less than 47 days for IgA and IgG and less than 29 days for light chain myelomas) had a bone marrow plasma cell labeling index significantly higher (P less than 0.01) than that of slow responders. Rapid responders had a median survival of 15 months, while slow responders had a median survival of 42 months (P less than 0.05). The difference in survival between the two groups was accounted for mainly by the difference in duration of first response and the different rates of MC increase following it. Both of these parameters were directly related to the half-life of MC decrease at response in IgA and IgG myelomas. The duration of second response and the half-life of MC increase following it were shorter than the duration of first response and than the half-life of MC increase at first relapse.