Incidence and risk factors for thalidomide neuropathy: a prospective study of 135 dermatologic patients.

Thalidomide is effective in several cutaneous diseases. Peripheral neuropathy is the most important adverse event limiting its use. Its incidence rate and its relation to thalidomide doses remain unclear. We prospectively monitored 135 patients treated with thalidomide for various dermatologic diseases for 2 y in order to estimate the annual incidence rate and risk factors for neuropathy. Patients underwent standardized neurologic examination and nerve conduction studies prior to, and regularly during treatment. Risk factors for neuropathy were assessed using a Cox proportional-hazards model. Clinical and electrophysiologic evidence of a thalidomide-induced neuropathy were present in 25.2% of the patients; however, when considering all potential cases, this rate reached 55.6%. The incidence rate was maximal during the first year of treatment (20%). The risk of neuropathy was related to the daily dose whatever the duration of treatment (p<10-3). Considering a daily dose < or =50 mg per day as reference, the relative risk for thalidomide neuropathy was 8.2 for a daily dose comprised between 50 and 75 mg per day and 20.2 for a daily dose >75 mg per day (p<10-3). No neuropathy occurred for daily doses < or =25 mg per day. The neuropathy was subclinical in nearly a quarter of patients with such an adverse event. These data confirm the high rate of thalidomide neuropathy and identify the daily dose as the main risk factor. The risk of neuropathy seems to be negligible for doses less than 25 mg per day, whatever the duration of therapy.