ESTRO 2023 - Abstract Book

S1162

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ESTRO 2023

Conclusion Elevation in PLR before initiation of CRT may be useful biomarker for predicting clinical outcomes.

PO-1436 The Dosimetric Implications of Sentinel Node Mapping on Adjuvant Radiotherapy for Endometrial Cancer

T. Charlton 1 , A. Ganguli 2 , N. Gomes 3 , K. Mackay 4 , A. Taylor 5

1 The Royal Marsden NHS Foundation Trust , Clinical Oncology , London, United Kingdom; 2 The Royal Marsden NHS Foundation Trust , Radiotherapy, London , United Kingdom; 3 The Royal Marsden NHS Foundation Trust , Surgery , London , United Kingdom; 4 The Royal Marsden NHS Foundation Trust, Clinical Oncology, London, United Kingdom; 5 The Royal Marsden NHS Foundation Trust, Clinical Oncology, London , United Kingdom Purpose or Objective Most patients with endometrial cancer present early and are treated with surgery. Adjuvant therapy is determined according to recent ESGO-ESTRO-ESP guidelines (1). Those in the High-intermediate and High-risk groups are offered a combination of radiotherapy (EBRT), vaginal vault brachytherapy (VVB), with or without chemotherapy. Sentinel Lymph Node (SLN) mapping is increasingly used to determine which patients may benefit from adjuvant EBRT. SLNs may be located beyond the pelvis and in those with involved pelvic nodes, 51% may also have involved para-aortic (PA) nodes (2). Traditional EBRT target volumes with a superior border of L5/S1 may not provide adequate coverage. This study maps SNL location and considers the dosimetric impact of extending target volumes to include the common iliac and PA regions. Materials and Methods 39 patients who received EBRT with or without VVB between January 2020 and February 2022 were included. Pre-operative imaging and SLN biopsies were used to map the location of primary station and involved lymph nodes. 10 consecutive patients who were scanned to a superior extent of T12 were identified. Target volumes were contoured to include the traditional pelvic volume (CTV A), extended to include the pre-sacral and common iliac region (CTV B) and the PA region (CTV C). A 5mm margin was added to create PTV A-C respectively.