Among patients with advanced melanoma who were treated with ipilimumab, about 20%-26% survived to 3 years, and these patients are likely to have a good long-term outcome, according to a pooled analysis of survival data published online Feb. 9 in the Journal of Clinical Oncology.

Investigators pooled data from ten prospective (including two phase III trials) and two retrospective studies with a total of 1,257 previously treated and 604 treatment-naive patients. At least 3 years after receiving ipilimumab, 254 patients were still alive, with a median follow up for this subset of 69 months. Around year 3, the Kaplan-Meier overall survival (OS) curve began to plateau and extended to 9.9 years for the longest survival follow-up.

“These results suggest that the majority of patients who reached this milestone time point had a low risk of death thereafter,” wrote Dr. Dirk Schadendorf and his associates (J. Clin. Oncol. 2015 Feb. 9 [ doi:10.1200/JCO.2014.56.2736 ]).

Compared with patients who were previously treated, treatment-naive patients had a higher median overall survival (13.5 months [95% confidence interval, 11.9-15.4] vs. 10.7 months [9.6-11.4]) and higher 3-year-survival rates (26% [21%-30%] vs. 20% [18%-23%]). No definitive conclusion could be drawn from this observation, however, since nonrandomized subsets were used for this analysis. Subset analysis by dose showed similar median OS and 3-year survival rates for ipilimumab 3 mg/kg, 10 mg/kg, and other dosing regimens.

The researchers expanded the study to include overall survival (OS) data from 2,985 patients enrolled in a U.S. multicenter, open-label, expanded-access treatment protocol (EAP). This group included patients with poorer prognostic factors, some of whom were ineligible for clinical trials. The expanded group showed a lower median OS of 9.5 months and 3 year–survival rate of 21%, with the familiar OS curve plateau around 3 years that extended up to 10 years in some patients.

While this analysis only examined overall survival rates, individual ipilimumab studies that tracked patient responses to the drug have shown that some proportion of long-term survivors did not achieve a response. Identifying the specific disease characteristics of the long-term survivors will require further study.

“Considering the historic median OS of approximately 8-10 months and a 5-year survival rate of approximately 10% in advanced melanoma, the results presented herein are encouraging for patients diagnosed with this aggressive disease,” the authors wrote.