Assessment of nodal status by 18F-FDG PET/CT in early stage ovarian cancer

Objectives In early stage ovarian cancer, lymph node (LN) metastases occur in approximately 5-25%. A non-invasive modality that allows an accurate LN staging could reduce unnecessary surgical procedures, reducing morbidities. Aim of this study was to evaluate the accuracy of 18F-FDG PET/CT in the detection of LN metastases in clinical early stage ovarian cancer.

Methods 68 pts (49 years; range 35-72) with a macroscopic tumor limited to the pelvis at standard staging procedure (clinical stage I-IIc), underwent preoperative FDG-PET/CT scan followed by total hysterectomy, bilateral salpingo-oophorectomy, omentectomy, random peritoneal biopsies and systematic pelvic and abdominal lymphadenectomy. The mean number of dissected LNs was 46 per pt. PET/CT images were analyzed and correlated to histological findings of LN status according to pt-based and lesion-based analyses.

Results PET/CT resulted negative at LN level in 57/68 pts (55 TN, 2 FN) and positive in 11/68 pts (10 TP, 1 FP). Incidence of LN metastases resulted 18%. On pt-based analysis, sensitivity, specificity, accuracy, negative and positive predictive value of PET/CT in detecting LN metastases were 83%, 98% 96%, 97%, 91% respectively. On a lesion-based analysis, considering overall 517 LN-sites, these values were 76%, 99%, 98%, 99%, 88%, respectively.

Conclusions In clinical early stage ovarian cancer FDG PET/CT is an accurate tool for the nodal status assessment. Its high negative predictive value (97%) could be useful in selecting pts who may be spared lymphadenectomy. As PET/CT can accurately detect LNs metastases, it could be of help for an optimal surgical debulking.