TA90 immune complex predicts survival following surgery and adjuvant vaccine immunotherapy for stage IV melanoma

Although prognosis remains poor for patients with distant metastatic melanoma, we have observed significantly prolonged survival in patients receiving our polyvalent melanoma cell vaccine (PMCV) following complete metastasectomy for American Joint Committee on Cancer (AJCC) stage IV melanoma. Clinical prognostic factors specific to this stage IV subgroup have not been well characterized. We previously reported that the serum immune complex (IC) level of a 90-kD glycoprotein antigen (TA90) was an objective predictor of survival and recurrence in patients with early-stage melanoma. In the present study we correlated the postoperative TA90-IC level of AJCC stage IV patients prior to adjuvant PMCV therapy with their duration of subsequent survival.

From October 1, 1984, to December 31, 1995, 125 stage IV patients began PMCV after complete resection of distant melanoma metastases. One blood sample was obtained immediately prior to vaccine therapy, and the serum TA90-IC level was assessed as positive or negative using our double-determinant ELISA. Disease-free and overall survival were recorded prospectively from the start of vaccine therapy. The correlation between prevaccine TA90-IC level and survival was assessed by the log-rank test and Cox proportional hazards model.

Median follow-up after PMCV therapy was 36.5 months, with a minimum of 12 months. Univariate analysis demonstrated that TA90-IC level is significant for both overall survival and disease-free survival. Median overall survival, median disease-free survival, and rate of 5-year survival were higher for patients with negative TA90-IC levels than for those with positive TA90-IC level (58 vs 19 months, 7 vs 4 months, and 49% vs 27%, respectively). Multivariate analysis established TA90-IC as an independent prognostic indicator for both overall and disease-free survival following adjuvant PMCV therapy for AJCC stage IV melanoma.

Prevaccine TA90-IC level correlated strongly with overall and disease-free survival in our stage IV melanoma patients receiving postoperative PMCV immunotherapy. This is the first serum marker shown to have importance in predicting the survival of melanoma patients receiving adjuvant immunotherapy after complete resection of distant metastases.