(ChemotherapyAdvisor) – Patients with ulcerated melanoma and lower tumor burden had the “greatest benefit” from treatment with adjuvant pegylated interferon alfa-2b (PEG-IFN-α-2b) compared with observation in resected stage III disease, investigators reported in the Journal of Clinical Oncology online September 24.

Long-term median 7.6-year follow-up of the randomized phase 3 EORTC 18991 trial in 1,256 patients, “the largest adjuvant melanoma trial to date,” found that adjuvant PEG-IFN-α-2b had sustained improvement on recurrence-free survival, the primary endpoint, noted Alexander M.M. Eggermont, MD, PhD, Institute Gustave Roussy, Villejiuf, France, and colleagues.

The 7-year recurrence-free survival rate was 39.1% in the PEG-IFN-α-2b arm vs 34.6% in the observation arm. These results were “marginally significant and slightly diminished” compared with the median follow-of of 3.8 years, data on which the US Food and Drug Administration approved PEG-IFN-α-2b in 2011 for resected melanoma.

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In the overall population, no significant increase in distant metastasis-free survival or overall survival (OS; P<0.57) was observed.

In patients with stage III-N1 ulcerated melanoma, treatment with PEG-IFN-α-2b was found to prolong recurrence-free survival, (HR 0.72; 99% CI, 0.46–1.13; P=0.06), distant metastasis-free survival (HR 0.65; 99% CI, 0.41–1.04; P=0.02), and OS (HR 0.59; 99% CI, 0.35–0.97; P=0.006)

A total of 37% of patients discontinued PEG-IFN-α-2b due to toxicity.

“As tested in EORTC 18991, PEG-IFN-α-2b has recurrence-free survival benefits that seem to be confined to the subpopulation of patients with microscopic nodal disease for whom it could therefore be offered to patients who cannot undertake HD IFN-α2b,” an accompanying editorial noted. “What is critically lacking is new insight into the optimal duration of therapy and predictors of which patients may derive the greatest benefit from therapy, and EORTC 18991 has not shed new light on this question, which was the initial impetus for this trial.”