Evaluation of assays to detect immune complexes as an immunodiagnostic aid in patients with melanoma.

Sera from 211 melanoma patients were tested before and after surgery for the presence of immune complexes (i.c.) by the 125I-C1q radioimmunoassay (C1q RIA) and a nephelometric monoclonal rheumatoid factor assay (mRhF). The patients were grouped according to stage of disease and therapy. Before surgery stage III patients had a higher incidence of i.c. (26.9%) than stage II (17.5%) and stage I (6.1%) patients. The incidence of i.c. in the latter patients did not differ from that of normal controls. Stage I patients treated with BCG therapy had a higher incidence of i.c. before and after surgery to remove melanoma compared with untreated patients. The incidence of i.c. in stage I and II patients was higher in sera taken after surgical removal of tumour compared to that in sera taken before surgery. Sequential studies revealed that i.c. often appeared then disappeared prior to clinical detection of recurrences. These results suggested that antigen excess was a frequent cause for failure to detect i.c. A prospective evaluation of the usefulness of assays for i.c. to monitor disease activity in melanoma patients was conducted. In some individual patients detection of i.c. was a prelude to recurrence from melanoma but the high false negative rate and the presence of elevated i.c. levels unrelated to recurrent tumour suggested that these assays wound be of limited diagnostic value in the management of melanoma.