Extramedullary multiple myeloma escapes the effect of thalidomide

Thalidomide is an antiangiogenic drug that produces a response rate ranging from 32 to 64% in patients with refractory/relapsed multiple myeloma (MM). However, the efficacy of thalidomide in patients with soft-tissue plasmacytomas is controversial. The aim of this study was to assess the response rate to thalidomide in patients with advanced MM and to correlate the response rate with the presence of extramedullary involvement.

Thirty-eight patients with refractory/relapsed MM were treated with thalidomide. Eleven patients had extramedullary involvement when therapy was initiated. The response rate was evaluated according to the criteria of the European Group for Blood and Marrow Transplantation.

Sixteen of the 38 patients (42%) responded to thalidomide. The response rate was significantly higher in patients without extramedullary involvement (59% vs 0%, p=0.0006). Although four of the 11 patients with extramedullary involvement had a serological response, a progression of the soft-tissue masses was observed in all of them.

Thalidomide is effective in patients with advanced MM. However, extramedullary disease does not respond to thalidomide, as delivered in this series. The mechanisms to explain different response to therapy depending on tumor homing warrant further investigation.