EP133/#395 Usefulness of pre-operative pet-ct in patients with endometrial cancer undergoing sentinel lymph node mapping: do negative findings on pet-CT negativity really indicate node negativity?

Objectives

We investigated the utility of Positron emission tomography-Computed tomography (PET-CT) in the setting of two different sentinel lymph node (SLN) mapping techniques; the conventional cervical injection method (one-step) and the fundal injection followed by cervical injection (two-step).

Methods

Patients with endometrial cancer undergoing FDG PET-CT followed by laparoscopic or robotic surgical staging with SLN mapping at the Yonsei Cancer Center between July 2014 and April 2021 were stratified into the PET-positive group (with suspected or likely lymph nodes metastasis) and PET-negative group. A chart review was performed to assess the number of SLNs harvested, patterns of SLN metastases, and recurrence.

Results

Among 466 patients undergoing one-step (n=276) and two-step (n=190) SLN mapping, LN metastasis was identified in 18 of 32 PET-positive patients. The sensitivity and specificity of PET-CT for diagnosing nodal metastasis were 46.2% and 96.7%, respectively. Among PET-positive patients with LN metastasis, anatomical distribution was concordant in 77.8% of patients. Among PET-negative patients, four (2.3%) had metastatic para-aortic SLNs, including three (1.7%) with isolated para-aortic metastases. Metastatic para-aortic SLNs were not seen in one-step patients. Among PET-positive patients, para-aortic SLN metastasis was identified in 35.7% of two-step and 16.7% of one-step patients. Among the 21 false PET-negative patients, recurrence was seen in four (19%) after a median follow-up of 34 months (range: 7–70).

Conclusions

PET-CT showed moderate sensitivity and high specificity. The SLN metastasis pattern, especially at the para-aortic level, indicates that the two-step SLN technique might be useful in both PET-negative and PET-positive patients.