Rao, R. D.

8530 Background: Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose limiting complication of chemotherapy. Lamotrigine (an anti-convulsant drug) appears to have some benefit when used to treat pain from neuropathy due to various etiologies. Based on these data, we conducted a phase III randomized placebo controlled study to determine the efficacy of lamotrigine in treating symptoms from CIPN. Methods: Patients with CIPN for 1 month or more were randomly assigned to lamotrigine (target dose 300 mg/day, increased by 50 mg/2 weeks) or placebo for 10 weeks. The co-primary endpoints were differences in average CIPN symptoms assessed by pro-rated area under the curve (AUC) of a numerical pain rating scale (NRS) and the Eastern Cooperative Oncology Group sensory neuropathy (ESN) scale. Accrual of 60 patients per group provided t-tests with 80% power to detect a difference of 0.57 standard deviation for each co-primary endpoint (moderate effect size) with a type I error of 0.025. Results: 131patients were enrolled, with complete data available for analysis in 93 (72%). Analyses were limited to this cohort but will be updated. Chemotherapy drugs considered to be causative of the CIPN were vinca alkaloids (30%), taxanes (25%), platinum-agents (7%), combinations (34%), and others (3%). Patients were equally matched with regards to baseline characteristics. Patients who enrolled had severe symptoms, with a baseline median ESN at enrollment of 3 (out of 3) in both groups. Toxicities were similar in both groups, however, more patients discontinued lamotrigine due to toxicities/refusals than those on placebo (32% vs 13% resp; p=0.04) and were therefore less likely to complete the 10 weeks therapy (60% vs. 78% resp, p=0.08). Average AUC of NRS score for patients on lamotrigine and placebo was 30.5 and 33.7 resp (p=0.48). The corresponding average AUC of the ESN scores were 12.4 and 14.5 (p=0.23). The proportions of patients with a 10 point (of 100) improvement in worst pain score (39% vs 36%) and a 1 point change in ESN (25% vs 27%) were similar between the lamotrigine and placebo arms, resp. Conclusions: These results suggest that lamotrigine is not effective for managing pain and symptoms due to CIPN. No significant financial relationships to disclose.