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#955 The value of intraoperative sentinel lymph node analysis using OSNA technique in EC
  1. Julene Saornil,
  2. Mikel Gorostidi,
  3. Marina Matute,
  4. Itziar Gonzalez,
  5. Ruben Ruiz,
  6. Juan Cespedes,
  7. Ibon Jaunarena,
  8. Paloma Cobas and
  9. Arantxa Lekuona
  1. Donostia University Hospital, Donosti, Spain


Introduction/Background Sentinel Lymph Node Biopsy (SLNB) is effective for assessing lymph node status in endometrial cancer (EC). When sentinel lymph node (SLN) is not detected, lymphadenectomy is required to determine lymph node involvement. Intraoperative frozen section examination has low sensitivity, but the One Step Nucleic Acid Amplification (OSNA) technique offers a definitive diagnosis. Knowledge of the lymph node status of removed SLNs helps determine the need for lymphadenectomy in undetected areas, avoiding unnecessary surgery. Our objective is to present an algorithm minimizing lymphadenectomy in EC patients with undetected SLN.

Methodology We analysed 116 patients who underwent SLNB for EC between January 2021 and January 2023. We studied cases requiring OSNA based on detection rates, CK19 positivity and feasibility. Patients were stratified by preoperative risk profile, including molecular profile.

OSNA is performed in CK19(+) patients, influencing the decision to perform or omit lymphadenectomy. Omitting lymphadenectomy is justified when OSNA is positive, as it does not affect prognosis or treatment decision in undetected areas.

OSNA also aided in assessing aortic lymph node involvement in adjusting radiation fields for stage IIIC1 in the low-risk group.

Results Out of 116 patients, 55 were low-risk and 59 high/intermediate risk preoperatively.

Among patients with high/intermediate risk, which represents the most relevant group, 9 lacked bilateral pelvic lymphatic detection, so OSNA was performed. Additionally, 15 had aortic detection without pelvic detection.

Between low-risk patients, two had no pelvic detection, with one lacking aortic level detection and the other skipping aortic SLN search. Among the remaining 8 low-risk patients without bilateral pelvic detection, 6 had aortic detection, enabling selective OSNA.

Approximately 12.9% of the series could benefit from the lymph node status knowledge, with 56% eligible for intraoperative OSNA.

Conclusion Intraoperative OSNA reduces the need for lymphadenectomy in EC patients with undetected sentinel lymph nodes.

Disclosures No disclosures.

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