Polymerase chain reaction detection of melanoma cells in the circulation: relation to clinical stage, surgical treatment, and recurrence from melanoma.

The detection of melanoma cells in the circulation by polymerase chain reaction (PCR) assays has been shown by several investigators to correlate with the stage of the disease and possibly with prognosis. We performed prospective studies on 276 patients with primary melanoma and regional lymph node (LN) metastases to assess the predictive value of PCR detection of tyrosinase and melanoma antigen recognized by T cells-1 (MART-1) in the blood for recurrence of melanoma. PCR tests for gp 100, Muc-18, and p97 reacted with RNA in blood from healthy subjects and were considered unsuitable for patient monitoring. The tests were most frequently positive in the first 3 months after surgery. There were 47 recurrences in 123 patients who had been followed up for 18 months. Assays within 3 months of surgery predicted recurrence from melanoma in 66% of the latter (tests for tyrosinase alone detected 51% and MART-1 alone 21% of the patients). Hence, 34% of recurrences were not predicted by tests in the early postoperative period. This did not appear to be because of marker-negative melanoma because summation of tests over the first year identified 89% of those with recurrent disease. Positive tests were recorded in 35% of patients who remained disease free, but it is too early to assess whether these represent false-positive results. The false-negative results raise the question of whether the assays will provide a reliable basis for selection of patients for adjuvant therapy.