Introduction/Background Ultrastaging is accurate in detecting nodal metastases but increases costs and may not be necessary in certain low-risk subgroups. We examine the risk of nodal involvement detected by sentinel lymph node (SLN) biopsy in the overall population of apparent early-stage endometrial cancer (EC) and stratified by histopathologic characteristics. Furthermore, we aim to identify a subgroup in which ultrastaging may be eliminated.
Methodology We retrospectively included patients who underwent SLN (with bilateral mapping and no empty nodal packets on final pathology)±systematic lymphadenectomy for apparent early-stage EC from 10/2013 through 12/2020. Lymph node status was determined by SLN only, regardless of non-SLN findings. The incidence of macrometastasis, micrometastasis, and isolated tumor cells (ITC) was measured in the overall population and after stratification by histotype (endometrioid vs. serous), myometrial invasion (MI; none, <50%, ≥50%), and grade. Proportions are reported as percentages[95% confidence interval(CI)].
Results Bilateral SLN mapping was accomplished in 1113 patients: 936 endometrioid and 177 non-endometrioid, of which 98 were serous. The incidence of macrometastasis, micrometastasis, and ITC was 4.0%[95%CI 2.9–5.3], 3.1%[95%CI 2.2–4.3], and 4.7%[95%CI 3.5–6.1], respectively. In patients with endometrioid histology (n=936), there were 2.9% macrometastases[95%CI 1.9–4.2], 2.7% micrometastases[95%CI 1.7–3.9], and 5.2% ITC[95%CI 3.9–6.9]. No nodal metastases were found in a subset of 178 patients with low-grade (G1–2) endometrioid EC without MI. The incidence of micro/macrometastasis increased to 1.9% [95%CI 0.9–3.5] in 516 patients with low-grade endometrioid EC invading <50% of the myometrium. In patients with serous histology (n=98), the incidence of macrometastases, micrometastasis, and ITC was 12.2%[95%CI 6.5–20.4], 7.1%[95%CI 2.9–14.2], and 2.0%[95%CI 0.2–7.2]. For serous carcinoma without MI (n=30), 2 out of 30 patients had micrometastases for an incidence of 6.7%[95%CI 0.8–22.1].
Conclusion Ultrastaging may be safely omitted in patients with low-grade endometrioid EC without MI. No other subgroups with a risk of nodal metastasis of less than 1% have been identified.
Disclosures Nothing to disclose.
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