Importance
Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) blockade with ipilimumab prolongs survival in metastatic melanoma patients. CTLA-4 blockade and granulocyte-macrophage colony stimulating factor (GM-CSF) secreting tumor vaccine combinations demonstrate therapeutic synergy in pre-clinical models. A key issue is whether systemic GM-CSF synergizes with CTLA-4 blockade.
Objective
To compare the effect of sargramostim plus ipilimumab vs ipilimumab alone on overall survival in patients with metastatic melanoma.
Design, Setting, and Participants
A phase II randomized clinical trial was conducted in the United States by Eastern Cooperative Oncology Group between December 28, 2010 and July 28, 2011. Patients with unresectable stage III or IV melanoma, ≥one prior therapy, no CNS metastases, and ECOG performance status 0/1 were eligible.
Interventions
Patients were randomized to ipilimumab 10 mg/kilogram intravenously day 1 plus sargramostim 250 μg subcutaneously days 1-14 of 21 day cycles versus ipilimumab alone. Ipilimumab treatment included induction for four cycles followed by maintenance every fourth cycle.
Main Outcomes and Measures
Primary was comparison of the length of overall survival. Secondary was progression-free survival, response rate, safety, and tolerability.
Results
A total of 245 patients were treated. Median follow-up was 13.3 months (range; .03-19.9). Median overall survival for sargramostim plus ipilimumab was 17.5 months (95% CI; 14.9, not reached) compared to 12.7 months (95% CI; 10.0, not reached) for ipilimumab. One-year survival rate for sargramostim was 68.9% (95% CI; 60.6%, 85.5%) compared to 52.9% (95% CI; 43.6%, 62.2%) with ipilimumab (stratified logrank one-sided P=.01; mortality hazard ratio .64, one-sided 90% repeated CI (not applicable, .90)). A planned interim analysis was conducted at 69.8% (104 observed/ 149 planned deaths) information time. O'Brien-Fleming boundary was crossed for improvement in overall survival. There was no difference in progression-free survival. Median progression free survival for ipilimumab+sargramostim was 3.1 months (95% CI; 2.9, 4.6) and for ipilimumab was 3.1 months (95% CI; 2.9, 4.0). Grade 3-5 adverse events occurred in 44.9% (95% CI; 35.8%, 54.4%) of sargramostim plus ipilimumab and 58.3% (95% CI; 49.0%, 67.2%) of ipilimumab alone (two-sided P=.04).
Conclusion and Relevance
Among patients with unresectable stage III or IV melanoma, treatment with sargramostim plus ipilimumab, compared to ipilimumab alone, resulted in longer overall survival and lower toxicity, but no difference in progression free survival. These findings require confirmation in larger sample sizes and longer follow up.