Should all patients with melanoma between 1 and 2 mm Breslow thickness undergo sentinel lymph node biopsy?

Sentinel lymph node (SLN) biopsy generally is recommended for patients who have melanoma with a Breslow thickness > or = 1 mm. Most patients with melanoma between 1 mm and 2 mm thick have tumor-negative SLNs and an excellent long-term prognosis. The objective of the current study was to evaluate prognostic factors in this subset of patients and determine whether all such patients require SLN biopsy.

Patients with melanoma between 1 mm and 2 mm in Breslow thickness were evaluated from a prospective multi-institutional study of SLN biopsy for melanoma. Disease-free survival (DFS) and overall survival (OS) were evaluated by Kaplan-Meier analysis to compare patients with melanoma that measured from 1.0 mm to 1.59 mm (Group A) versus patients with melanoma that measured from > or = 1.6 mm to 2.0 mm thick (Group B). Univariate and multivariate analyses were performed to evaluate factors predictive of tumor-positive SLN status, DFS, and OS.

The current analysis included 1110 patients with a median follow-up of 69 months. SLN status was tumor-positive in 133 of 1110 patients (12%) including 66 of 762 patients (8.7%) in Group A and 67 of 348 patients (19.3%) in Group B (P < .0001). On multivariate analysis, age, Breslow thickness, and lymphovascular invasion were independently predictive of a tumor-positive SLN (P < .05). DFS (P < .0001) and OS (P = .0001) were significantly better for Group A than for Group B. When tumor thickness was treated as either a continuous variable (P < 0.0001) or a categorical variable (P < .0001), it was significantly predictive of DFS and OS. On multivariate analysis, Breslow thickness, age, ulceration, histologic subtype, regression, Clark level, and SLN status were significant factors predicting DFS; and Breslow thickness, age, primary tumor location, sex, ulceration, and SLN status were significant factors predicting OS (P < .05). A subgroup of patients who had tumors <1.6 mm in Breslow thickness, had no lymphovascular invasion, and were aged > or = 59 years had a low risk (5%) of tumor-positive SLN.

The current findings indicated that there is significant diversity in the biologic behavior of melanoma between 1 mm and 2 mm in Breslow thickness. SLN biopsy is recommended for all such patients to identify those with lymph node metastasis who are at the greatest risk of recurrence and mortality.