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#56 Incidence of sentinel lymph node metastases in apparent early-stage endometrial cancer
  1. Luigi ADe Vitis1,2,
  2. Diletta Fumagalli1,
  3. Ilaria Capasso1,
  4. Leah Grcevich1,
  5. Gabriella Schivardi1,2,
  6. Francesco Multinu1,2,
  7. Tommaso Occhiali1,
  8. Ilaria Betella2,
  9. Maryam Shahi3,
  10. Angela J Fought4,
  11. Michaela EMc Gree4,
  12. Nicoletta Colombo2,5,
  13. Vanna Zanagnolo2,
  14. Giovanni D Aletti2,6,
  15. Carrie L Langstraat1,
  16. Andrea Mariani1 and
  17. Gretchen E Glaser1
  1. 1Department of Obstetrics and Gynecology, Mayo Clinic, Rochester, USA
  2. 2Department of Gynecologic Oncology, European Institute of Oncology, Milan, Italy
  3. 3Department of Pathology, Mayo Clinic, Rochester, USA
  4. 4Division of Clinical Trials and Biostatistics, Mayo Clinic, Rochester, USA
  5. 5University of Milano-Bicocca, Faculty of Medicine and Surgery, Milan, Italy
  6. 6University of Milan, Department of Oncology and Hemato-Oncology, Milan, Italy


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].

Abstract #56 Table 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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