Thalidomide in multiple myeloma: lack of response of soft-tissue plasmacytomas.

Thalidomide is active in patients with refractory myeloma. Seventeen patients (nine men/eight women, median age 73 years) with multiple myeloma (MM) were treated with thalidomide. Fifteen patients had refractory disease and two untested relapse. The median dose of thalidomide was 500 mg (range, 200-800 mg). Nine of the 17 patients (53%) responded. The response rate was significantly higher in patients with no extramedullary disease than in those with soft tissue masses (75% CI: 43-95% versus 0%; P = 0.01)). Of note, no decrease in the size of soft tissue plasmacytomas was observed in all the five patients who had extramedullary involvement. This data suggests that the mechanism of action and effectiveness of thalidomide might depend on the site of the tumour cells.