Whole-body [18F]fluoro-2-deoxyglucose positron emission tomography scan as combined PET-CT staging prior to planned radical vulvectomy and inguinofemoral lymphadenectomy for squamous vulvar cancer: a correlation with groin node metastasis.

Surgery is the mainstay of treatment for vulvar cancer. FIGO staging requires histopathological detail of the primary tumor and inguinofemoral lymph nodes but groin node dissection carries a substantial risk of short and long-term morbidity. The trend in current practice is towards sentinel lymphadenectomy for cancers with a low risk of metastases. Full lymphadenectomy is undertaken if the sentinel lymph node contains metastasis. The predictive value of 18F-FDG-PET in preoperative assessment of the groin in vulvar squamous cancer was assessed in retrospect at a single institution. A period of three years prior to the introduction of sentinel lymph node mapping was chosen in order to have full histopathological assessment of inguinal and femoral lymph nodes available as the gold standard for correlation with positron emission tomography-computerized tomography (PET-CT) to determine the accuracy of the enhanced radiological technique. In patients with histologically proven metastases to groin nodes, comparisons between PET-CT positive (True-positive/TP) and negative (False-negative/FN) groups vis-à-vis histology showed a tendency towards higher FDG avidity in the vulvar lesions, more bilateral nodes, multiple metastases, larger metastases and more extra-capsular extension in the TP group. Calculations per patient for PET-CT yielded a sensitivity of 50% and specificity at 100%. The positive predictive value (PPV) was 100% and the negative predictive value (NPV) was 57.1%. The test accuracy was 70% per patient. The high positive predictive value of PET-CT can be used to advance treatment planning prior to surgical staging of patients identified with Stage III disease. The poor sensitivity makes it unsuitable as a substitute for staging lymphadenectomy.