The Diagnostic Value of PET/CT Imaging in Melanoma Groin Metastases

Combined superficial (inguinal) and deep (iliac and obturator) groin dissection (CGD) is the standard treatment of patients with stage IIIB and IIIC melanoma groin metastases; however, the additional value of iliac lymphadenectomy is debated. In our institute, imaging with positron emission tomography/computed tomography (PET/CT) is part of the regular preoperative work-up. The aim of this study was to evaluate the diagnostic value of PET/CT in detecting iliac lymph node metastases.

This retrospective study included 70 melanoma patients with stage IIIB or IIIC melanoma and an indication for therapeutic CGD, who were treated at our institution between 2003 and 2013. Median disease-free survival (DFS) was 9 months and median follow-up time was 16 months. The results of PET/CT were compared with the results of pathological analysis after CGD. Additional quantitative analysis of PET/CT imaging was performed.

For superficial melanoma groin metastases, sensitivity of PET/CT was 97 %, specificity was 50 %, positive predictive value (PPV) was 90 %, and negative predictive value (NPV) was 71 %. For iliac lymph node metastases, sensitivity of PET/CT was 67 %, specificity was 91 %, PPV was 73 %, NPV was 81 %, and false negative rate was 33 %.

The results of this retrospective study indicate that PET/CT imaging could be a valuable method in preoperative work-up in this patient category; however, PET/CT alone should not be used as a tool to determine the extent of surgery, since one-third of patients with iliac lymph node involvement will be missed on PET/CT.