Identification of groin node metastasis in squamous cell vulval cancer using preoperative [18F] FDG-PET/CT. Can unnecessary lymphadenectomy be prevented?

INTRODUCTION: Vulval cancer is the 4th most common gynaecological cancer. The International Federation of Gynaecology and Obstetrics(FIGO) staging requires a histopathological dissection of the primary tumour and the inguinofemoral lymph nodes(IFLN).However, radiological methods of IFLN assessment often lack accuracy, leading to unnecessary IFLN dissections carrying significant morbidity.

AIM OF THE STUDY: To determine its accuracy of [18F] FDG-PET/CT as a pre-operative assessment tool for the groin lymph node in vulval squamous cell carcinoma.

METHODOLOGY: The predictive value of PET/CT in preoperative assessment of the groin node metastasis was assessed retrospectively in patients with vulval cancer, treated in St. James's Hospital Dublin (2010-2022). SUVmax of the nodal uptake of each inguinal area (if present) was calculated and correlated to histologically confirmed groin metastasis. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of PET/CT in predicating groin node metastasis were calculated. Overall survival was also calculated.

RESULTS: Out of the 200 patients 107(53.3%) had a full histopathological assessment of inguinal area and a PET/CT. Patients had either bilateral or unilateral IFLN histology, yielding 197 groins. The sensitivity of PET/CT for IFLN metastasis was 60.0% and specificity was 92.10%. The PPV was 74.30% and the NPV was 88.60 %. The mean SUVmax was 7(range 1.6-30.0 for metastatic nodes (true positive) and 2.18(range 1.9-3.1) for histologically negative nodes (false positive).

CONCLUSION: This study showed that PET/CT has a moderate sensitivity to identify those at risk of lymph node metastasis. Further prospective studies are required to validate the use of PET-CT in discriminating metastatic from non-metastatic IFLN.