Regional nodal metastatic disease is the strongest predictor of survival in patients with thin vertical growth phase melanomas: a case for SLN Staging biopsy in these patients.

BACKGROUND

The benefit of sentinel lymph node (SLN) biopsy for patients with thin (< or =1.0 mm) melanomas, even for prognostic value, is controversial. This may partly result from the relatively small number and short follow-up of SLN-positive patients in this group. Previously, we have shown that clinical regional nodal metastatic disease (RNMD) serves as a good surrogate for SLN positivity. Here, we use RNMD as a validated surrogate for SLN positivity and examine its prognostic value in a large pre-SLN group of patients with thin vertical growth phase (VGP) lesions who would today commonly be offered SLN biopsy in our practice.

METHODS

Between 1972 and 1991, 472 patients with thin VGP melanomas with at least 10 years' follow-up were eligible for the study. Kaplan-Meier survival curves were computed for patients with and without RNMD. A multivariate Cox model and classification tree analysis were used to evaluate clinical and histopathologic predictors of survival.

RESULTS

Sixty-seven patients (14.2%) developed recurrence, 53.7% of whom developed RNMD. Forty-five patients (9.5%) experienced melanoma-related deaths (MRD). The most statistically significant predictor of MRD was RNMD (hazard ratio [HR] 13.5, P < .0001). Thickness (HR 10.5, P = .004), axial location (HR 4.6, P = .001), and age >60 years (HR 2.7, P = .005) additionally were independently associated with an increased risk of MRD. RNMD patients demonstrated a 44.4% 10-year disease-specific mortality.

CONCLUSIONS

RNMD was the most statistically significant factor associated with MRD in patients with thin VGP lesions. This supports the prognostic use of SLN biopsy in this group, recognizing that additional factors, including thickness, axial location, and older age were independently associated with a worse survival outcome.