Pelvic lymph node dissection in metastatic melanoma to the groin should not be abandoned yet

In recent years there has been a plea to abandon the pelvic lymph node dissection in the treatment of patients with metastatic melanoma to the groin. A trend towards a conservative surgical treatment is already evolving in several European countries. The purpose of this study is to identify factors associated with pelvic nodal involvement, in order to improve selection of patients whom might benefit from a pelvic nodal dissection.

A retrospective analysis was performed on prospectively collected data concerning patients who underwent an inguinal lymph node dissection (ILND) with pelvic lymph node dissection for metastatic melanoma at the University Medical Center Groningen. Multivariable logistic regression analysis was performed to determine factors associated with pelvic nodal involvement. Diagnostic accuracy was calculated for ¹⁸F-FDG PET + contrast enhanced CT-scan and ¹⁸F-FDG PET + low dose CT-scan.

Two-hundred-and-twenty-six ILND's were performed in 223 patients. The most common histologic subtype was superficial spreading melanoma (42.6%). In patients with micrometastatic disease, 15.7% had pelvic nodal involvement vs 28.2% in patients with macrometastatic disease (p: 0.030). None of the characteristics known prior to the ILND, were associated with pelvic nodal involvement. Imaging methods were unable to accurately predict pelvic nodal involvement. Negative predictive value was 78% for ¹⁸F-FDG PET + low dose CT-scan and 86% for an ¹⁸F-FDG PET + contrast enhanced CT-scan.

There are no patient- or tumor characteristics available that can predict pelvic nodal involvement in patients with melanoma metastasis to the groin. As no imaging technique is able to predict pelvic nodal involvement it seems unjust to abandon the pelvic lymph node dissection.