Triple-marker PCR assay of sentinel lymph node as a prognostic factor in melanoma

Metastasis of sentinel lymph node (SLN) is generally evaluated on histopathological examination and controversy still exists over the usefulness of PCR assay of SLN.

To investigate the prognostic value of triple-marker PCR assay of SLN.

A total of 165 patients with primary cutaneous melanoma who underwent SLN biopsy were included. Clinical and histopathological data were retrieved from each patient's file and triple-marker PCR assay (tyrosinase, GP-100 and MART-1) was performed on the SLN as well as routine histopathological evaluation. PCR positivity was defined as the expression of all three PCR markers. To evaluate melanoma-specific survival (MSS) and disease-free survival (DFS), we used the Kaplan-Meier method and the log-rank test. Multivariate analyses using the Cox proportional hazards regression model were also performed.

Sentinel lymph nodes were identified in all 165 patients: 61 patients (37.0%) were male and 104 (63.0%) were female, with a mean age of 60.2 years. Of the 165 melanomas, 81 (49.1%) were acral lentiginous melanomas. Compared with the patients with PCR positivity (1-2 markers) or PCR negativity, patients with PCR positivity (3 markers) had significantly poor MSS (5-year survival rate, 58.7% vs. 84.4%; P < 0.0001) and DFS (5-year survival rate, 25.0% vs. 83.9%; P < 0.0001), with median follow-up of 42 months for MSS and 38 months for DFS. These survival rates of patients with PCR positivity (3 markers) were lower than those of patients with histopathologically positive SLN. In multivariate analysis, PCR positivity (3 markers) was an independent prognostic factor for both MSS (hazard ratio [HR], 2.81; 95% confidence interval [CI], 1.07-7.33; P = 0.035) and DFS (HR, 2.48; 95% CI, 1.08-5.69; P = 0.032).

The expression of three PCR markers was a significant prognostic factor for both MSS and DFS and might be closely correlated to a dismal prognosis.