Thalidomide in low doses is effective for the treatment of resistant or relapsed multiple myeloma and for plasma cell leukaemia.

Thalidomide is an effective treatment for relapsed multiple myeloma (MM), but is associated with a significant side effect profile at higher doses. In a recent study, only half of the enrolled patients were able to tolerate the maximum dose of 800 mg/day [Singhal, S., et al. (1999) "Antitumor activity of thalidomide in refractory multiple myeloma", New Engl. J. Med. 341, 1565-1571]. Moreover, the dose-response relationship has not been defined. We report our use of low dose thalidomide in a small cohort of 12 patients-eight with relapsed or refractory MM and four with plasma cell leukaemia (PCL). Five of the 12 (42%) patients had a partial response, showing a median fall in their PP/BJP of 80% (63-90%) at a median dose of 175 mg (100-300 mg) with negligible side effects. Three of four patients with PCL showed an impressive response to treatment with thalidomide as a single agent. No patient who failed to show any evidence of response at low dose (<150 mg/day) responded to higher doses. In this study, thalidomide induces a similar rate of response at a lower and better tolerated dose than previously reported and produced "best ever" responses in patients with resistant PCL.