Background: A phase III, randomized, double-blind, multi-institutional trial was performed evaluating active specific immunotherapy using vaccinia melanoma oncolysate (VMO) in the surgical adjuvant setting in patients with stage II melanoma (UICC staging). The first interim analysis showed no significant difference in disease-free and overall survival. The data were further analyzed to identify subsets of patients with improved outcome when treated with VMO.
Methods: Patients received either VMO or placebo of live vaccinia vaccine virus (V), once a week for 13 weeks and then once every 2 weeks for an additional 39 weeks or until recurrence. Having stratified patients according to sex, age, number of positive nodes, tumor thickness, and clinical stage, data were analyzed for disease-free survival and overall survival.
Results: Male patients showed a 17% difference in overall survival at 4 years when treated with VMO (p = 0.19). A subset of male patients < 57 years of age with one to five positive nodes showed a 30% difference at 4 years with VMO (p = 0.06). Patients with clinical stage I but pathological stage II disease (both male and female), who had undergone prophylactic node dissection, showed a 23% difference in survival at 3 years with VMO (p = 0.11).
Conclusions: This subset analysis shows encouraging survival benefit in certain subsets of patients and an increasing trend in overall survival. Further follow-up of this phase III trial from a second interim analysis will be forthcoming.