Pembrolizumab Active in Rare Advanced Mucosal Melanoma

The immunotherapy pembrolizumab was active in patients with advanced mucosal melanoma enrolled in a series of the KEYNOTE clinical trials, according to data (abstract 1142) presented at the European Cancer Congress 2017 by Marcus Butler, a medical oncology at the Princess Margaret Cancer Centre, Toronto, Canada.

In this pooled analysis, Butler and colleagues assessed outcomes of patients with advanced mucosal melanoma who were enrolled in the KEYNOTE-001, 002, and 006 clinical trials. On the studies, patients received pembrolizumab 2 mg/kg every 3 weeks, 10 mg/kg every 3 weeks, or 10 mg/kg every 2 weeks. Of the 1,567 patients in the trials, 84 (5%) had advanced mucosal melanoma.

“Sixteen of these patients (19%) responded to treatment with pembrolizumab, of whom 12 are still alive without their disease progressing and, so far, the longest time some of these patients have continued to be successfully treated is more than 27 months,” Butler said in a press release. “There are some patients with mucosal melanoma who have had complete responses to pembrolizumab and essentially return to a normal life. Some, of course, have less spectacular responses, but they still benefit from therapy.”

Pooled data from the trials showed that the overall response rate for patients with mucosal melanoma was 19%, with a disease control rate of 31%. Median progression-free survival was 2.8 months and the median overall survival was 11.3 months. Among the patients who experienced a response to pembrolizumab, the median time to response was 12.4 weeks.

Ninety percent of the patients with mucosal melanoma on these trials had received prior therapy; 39% had prior ipilimumab treatment. Looking at those patients with prior ipilimumab, the overall response rate was 15%, with a disease control rate of 27%. At follow-up, 80% of patients who responded were alive and progression free with a median duration of response of 27.6 months.

“In earlier studies, mucosal melanoma was excluded since it is a rare subtype,” Butler said. “These findings suggest that mucosal melanoma patients should be offered immunotherapy as standard of care and not excluded. Response rates may be a bit lower than for other types of melanoma, so further studies to improve benefit need to be conducted.”

Of the 1,483 patients in these KEYNOTE trials who had other forms of advanced melanoma and who received at least one dose of pembrolizumab, 33% responded to the treatment, 72% were still alive without their disease progressing, and the median overall survival time was nearly 2 years.