Are negative pelvic sentinel lymph nodes reflective of negative para-aortic nodes in high grade endometrial cancer? (071)

Abstract

<b>Objectives:</b> Whether pelvic sentinel lymph nodes (SLN) in highgrade endometrial cancers reflect the presence of para-aortic (PA) node metastasis is debated in the literature. It is unclear whether negative pelvic SLNs alone may be relied on as an indicator to omit chemotherapy aimed to prevent distant recurrence in high-grade histologies. The objective of this study was to determine the accuracy of pelvic SLNs in detecting positive PA lymph nodes in high-grade uterine cancer and to determine the recurrence rate in patients with high-grade uterine cancers who did not receive adjuvant chemotherapy based on negative pelvic SLNs. <b>Methods:</b> This was a retrospective review of patients with newly diagnosed, clinically uterine-confined high-grade endometrial cancer (grade 3 endometrioid, serous, clear cell, and carcinosarcoma) who underwent surgery at a single tertiary care institution between January 2015 and July 2020. Patients were included if they underwent pelvic SLNs +/- PA node dissection, no visible extrauterine disease intraoperatively, and final pathology revealed high-grade histology. Demographic, pathological, treatment, and outcome data collected were analyzed using descriptive statistics in STATA 14.0. <b>Results:</b> One hundred and twenty-one patients with surgery for high-grade endometrial cancer were identified. After applying exclusion criteria, 110 patients were included. The median age was 68.5 years (range: 37-90 years). The surgical staging was completed laparoscopically in 88.2% of patients. Grade 3 endometrioid, serous, clear cell, and carcinosarcoma accounted for 45.5%, 36.4%, 10.9%, and 7.3% of postoperative pathology, respectively. Bilateral mapping was achieved in 76.4% of patients. On final pathology, 63.7% were stage I, 10.9% were stage II, 1.8% were stage IIIA, and 23.6% were stage IIIC with positive nodes. Adjuvant radiation was given to 66.4%, whereas adjuvant chemotherapy was given to 24.5% of patients. Sixty-three patients had a PA lymph node dissection (56 bilateral, seven unilateral) in addition to the pelvic SLN. Among this group, 5.8% (95% CI: 1.2-16.0%) had positive PA node despite a negative pelvic SLN. These patients had serous or carcinosarcoma histology with outer half myometrial invasion, while only one patient had positive lymphovascular space invasion (LVSI). Among those with a negative pelvic SLN and no adjuvant chemotherapy (<i>n</i>=75), the distant recurrence rate was 14.7%. <b>Conclusions:</b> The rate of isolated PA node metastasis in high-grade endometrial cancers despite a negative pelvic SLN may be higher than the accepted published 1-3% incidence. More evidence is needed to characterize the accuracy of SLN alone in patients with high-grade histology. Adjuvant chemotherapy may require further tailoring based on additional factors outside the stage, such as molecular characterization of high-grade histologies, to improve patient outcomes.