Sentinel lymph node micrometastasis and other histologic factors that predict outcome in patients with thicker melanomas

Background: In patients with melanoma, lymph node staging information is ob tainable by the surgical techniques of lymphatic mapping and sentinel lymph node (SLN) biopsy Although no survival benefit has been proven for the pro cedure, the staging information is useful in identifying patients who may b enefit from further surgery or adjuvant therapy. Currently, however, it is not being recommended for patients with thick melanomas (>3-4 mm). The risk of hematogenous dissemination is considered too great in these patients. R ecent studies indicate, however, chat a surprising number of patients with thick melanomas become long-term survivors, and the lymph node status may b e predictive. None of the conventional microscopic features used to gauge p rognosis in patients with melanoma have proven helpful in distinguishing th e survivors with thick melanoma from those who will die of their disease. Objective: Our purpose was to evaluate the influence of SLN histology and o ther microscopic parameters on survival of patients with thick melanomas. Methods: A computerized patient database at the Cutaneous Oncology Clinic a t H. Lee Moffitt Cancer Center was accessed to obtain records on patients w ith melanomas thicker than 3.0 mm (AJCC T3b). A retrospective analysis was conducted with attention paid to histologic variables, sentinel node status , and survival. Survival curves were constructed with the Kaplan-Meier meth od, and a Cox-Mantel rank testing was used to establish statistical signifi cance. Results: Between 1991 and 1999, 201 patients were diagnosed with melanoma t hicker than 3.0 mm, and 180 were alive at an average follow-up of 51 months . Of these, 166 were alive without disease. The mean overall and disease-fr ee survival rates were 78% and 66%. respectively. There was a statistically significant difference in disease-free survival (3-year) between SLN-posit ive and SLN-negative patients (37% vs 73%, respectively; P = .02). The over all survival (3-year) for the SLN-positive patients was less than the node- negative patients (70% vs 82%), but it was not statistically significant (P = .08). The disease-free survival for patients with ulcerated lesions was less than for nonulcerated lesions (77% vs 93%, P = .05). None of the other histologic parameters studied, including Breslow thickness, Clark level, m itotic rate, or regression, had an influence on the overall or disease-free survival in this group of patients with thick tumors. Conclusions: The results indicate that the SLN node status is predictive of disease-free survival for patients with thick melanomas. A surprising numb er of patients in the study were free of disease after prolonged follow-up. None of the histologic features of the primary turner were helpful in pred icting outcome, except for ulceration. SLN biopsy appears to be justified f or prognostic purposes in patients with thick melanomas.