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

Abstract

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