Rescue-free laxation response with methylnaltrexone treatment in cancer patients with opioid-induced constipation: The impact of baseline ECOG status.

Abstract

e24083 Background: Opioid-induced constipation (OIC) is a common side effect of opioid treatment for cancer-related pain. Methylnaltrexone (MNTX) is a peripherally active µ-opioid receptor antagonist indicated for OIC that does not affect opioid central analgesia. We assessed if baseline Eastern Cooperative Oncology Group (ECOG) status impacted the rescue-free laxation (RFL) responses among cancer patients with OIC treated with repeated doses of MNTX. Methods: This pooled post hoc analysis from 2 randomized, placebo-controlled, institutional review board–approved clinical studies included cancer patients with OIC (study 302, NCT00402038; study 4000, NCT00672477). Study 302 compared subcutaneous MNTX 0.15 mg/kg vs placebo and study 4000 compared body weight‒based subcutaneous MNTX 8 mg (38–< 62 kg) or 12 mg (³ 62 kg) vs placebo. The data were stratified by baseline ECOG status (< 2 vs ≥ 2). Endpoints included the number of patients with RFL responses within 4 hours after ≥ 2 of the first 4 doses and the number of patients with RFL response within 4 hours of treatment for patients who received all 7 doses. Results: The intent-to-treat analysis included 43 patients with an ECOG < 2 (placebo = 20; MNTX = 23) and 187 patients with an ECOG ≥ 2 (placebo = 94; MNTX = 93). Those with an ECOG < 2 were younger (mean age 58 vs 65 years), predominantly male (60.5% vs 51.3%), and used a higher daily dose of oral morphine equivalent (190.7 vs 180.0 mg/d) compared with those with an ECOG ≥ 2. Cancer patients with an ECOG < 2 treated with MNTX had a significantly greater RFL response within 4 hours after ≥ 2 of the first 4 doses compared with placebo (56.5% vs 5.0%, P = 0.0003). Similar results were reported for patients with an ECOG ≥ 2 (57.0% vs 5.3%, P < 0.0001). Compared with placebo, the MNTX group had a greater proportion of patients with an RFL response, whether they had at least 1 RFL response or up to 7 RFL responses out of 7 doses, with significant treatment differences with each additional RFL per 7 doses among cancer patients with an ECOG ≥ 2 (Table). Conclusions: RFL response rates in cancer patients were significantly greater in the MNTX group vs the placebo group regardless of baseline ECOG status; responses were similar between the 2 groups despite a higher daily dose of opioids in the group with an ECOG > 2. Clinical trial information: NCT00402038; NCT00672477. [Table: see text]