Early responder myeloma: Kinetic studies identify a patient subgroup characterized by very poor prognosis

In order to assess the prognostic value of rapid tumor mass reduction in responding multiple myeloma (MM) patients, 100 consecutive patients were analyzed, and bone marrow plasma cell kinetic characteristics were evaluated at diagnosis. Forty-two patients obtained a tumor mass reduction ≥ 50% with three cycles of chemotherapy and within 3 months (early responder myeloma [ERM]), and 23 in > 3 months (slow responder myeloma [SRM]). Survival rates in these two groups were not statistically different (P = .07). The labeling index (LI) of bone marrow plasma cells was significantly higher in ERM patients than in SRM patients (1.8 ± 2.0 v 0.8 ± 0.7, P = .006). The LI was used to separate the ERM patients into two well-defined subgroups. ERM patients with a LI ≥ 2% showed a median survival of 16.4 months, whereas ERM patients with a LI < 2% did not reach the median survival at 46.9 months (P < .0044). Remission duration was also significantly different: 12.2 months in the high LI subgroup and 26.3 months in the low LI subgroup (P < .0025). Early response itself does not correspond to shorter remission duration and shorter survival, but it is a poor prognostic factor if associated with a high plasma cell proliferation activity.