Adjuvant radiotherapy for palpable melanoma metastases to the groin: when to irradiate?

Purpose: To determine the efficacy of and criteria for postoperative radiotherapy (PORT) in patients with palpable melanoma metastases to the groin.

Methods And Materials: Patients with palpable metastases to the groin who were treated with therapeutic nodal dissection during 2000 to 2006 were identified in a prospective institutional database.

Results: In 101 patients, 103 therapeutic nodal dissections were performed; 37 of these were treated with PORT to a median equivalent dose (eqTD(2)) of 50.6 Gy (range, 50-72 Gy). In the surgery-only and PORT groups, 2-year regional control rates were 86% (95% confidence interval [CI] 76-95%) and 91% (95% CI, 81-100%), respectively (p = 0.395). Of five recurrences in radiation-treated patients, four were of dermal type, and in three of these cases, no bolus over the operative scar was used. PORT improved 2-year regional control (46% [95% CI, 11-82%] vs. 82% [95% CI, 63-100%], p = 0.022) among patients in which the sum of risk factors present (i.e., risk factor score) was ≥2. In multivariate analysis, risk-factor score (<2 vs. ≥2: HR, 2.93; 95% CI, 1.00-8.56; p < 0.0001) and PORT (yes vs. no: HR, 7.81; 95% CI, 2.83-21.74; p = 0.050) was predictive for regional control and on logistic-regression testing, number of involved lymph nodes was predictive for systemic dissemination (p = 0.011).

Conclusions: PORT should follow therapeutic nodal dissection in cases with two or more adverse factors. More conventional fractionation (≤2.5 Gy), cumulative eqTD(2) <60 Gy and use of bolus over the operative scar are recommended.