Prognostic significance of leukocyte-dependent antibody activity in melanoma patients.

Sera from patients with melanoma and control subjects were examined for leukocyte-dependent antibody (LDA) activity against cultured melanoma and control nonmelanoma target cells in 51Cr release cytotoxicity assays. In over a third of 344 melanoma patients, LDA activity against melanoma cells was related to tumor growth, shown by disappearance of the LDA after surgical removal of melanoma. Tumor-related LDA activity was not detected in 143 controls with various nonmelanoma malignant conditions and benign skin lesions. Approximately 5% of the patients had high-titer melanoma LDA that was unchanged by surgical removal of the tumor, and 15% had melanoma LDA revealed in their sera only after the sera had been treated to dissociate immune complexes. In patients with stage I melanoma, the disease-free interval was significantly longer in those with tumor-related LDA compared to those with no LDA. Analysis of the data in relation to known prognostic variables suggested that the main influence of LDA on prolongation of the disease-free interval was in males. An association between tumor-related LDA and a longer disease-free interval was also apparent in patients with stage II melanoma at first presentation but not in those with recurrence after prior treatment of primary melanoma. The results suggest that LDA activity against melanoma cells in the sera of patients after surgical removal of stage I or stage II melanoma is a favorable prognostic factor. Further studies are needed to determine whether induction of melanoma LDA by immunotherapy may improve the outcome in patients without naturally occurring LDA.