ESTRO 2024 - Abstract Book

S1040

Clinical - Gynaecology

ESTRO 2024

dose levels were not reached. Nevertheless, based on the favourable early toxicity and response reports, the protocol will continue to recruit patients.

Offline target dose levels as achieved in the pretreatment plans were slightly higher than the achieved online target dose levels, whereas the limiting OAR doses were fairly similar. Several contributing factors may play a role. Firstly, due to the OAR dose prioritizing planning strategy, a unfavorable OAR position (e.g. caused by bladder and rectal filling) can lower the achievable target dose. Secondly, in the online setting, limited time is available to balance between target and OAR dose in the adapted plan. To alleviate this, we will monitor OAR doses online and prospectively adapt online constraints accordingly.

Keywords: MRLinac, boost, MARGARITA

1827

Poster Discussion

Adjuvant treatment in stage I-II serous endometrial cancer: a single institution 20-year experience

Rodrigo Cartes 1 , Aquila Akingbade 2 , François Fabi 3 , James M G Tsui 1 , Joanne Alfieri 1

1 McGill University, Radiation Oncology, Montreal, Canada. 2 Western University, Radiation Oncology, London, Canada. 3 Université Laval, Radiation Oncology, Québec, Canada

Purpose/Objective:

Serous endometrial carcinoma (SEC) is an infrequent but aggressive histologic subtype of uterine cancer. Historically, different adjuvant treatment strategies have been used to reduce the risk of recurrence of these patients, including chemotherapy (CT), pelvic external beam radiotherapy (WPRT), vaginal vault brachytherapy (VBT) and chemo-radiotherapy (CT+RT) in different combinations and sequencing. To date, there is no consensus on the optimal adjuvant treatment for stage I and II SEC. The aim of this retrospective review was to report the experience of a single Canadian institution in managing early-stage SEC with various adjuvant therapies, focusing on survival outcomes, patterns of recurrence, and toxicities.

Material/Methods:

A comprehensive retrospective review of the pathology database of the McGill University Health Centre (MUHC) was conducted to identify all the cases of stage I-II FIGO 2009 SEC treated between 2002 and 2019. Demographics of the population, pathology characteristics, adjuvant treatment details, survival status, recurrence status, recurrence characteristics and acute, and late toxicities as per CTCAE v4.0 were recorded up to September 2023. Kaplan-Meier estimates, and Cox’s Proportional Hazard model were used to calculate overall survival (OS) and Disease-Free Survival (DFS). Analysis was done using the lifelines library version 0.27.8 in Python v3.10.12. The rest of the variables were analyzed using descriptive statistics.

Results:

Between 2002 and 2019, 50 patients with stage I-II SEC were treated at the MUHC. All patients underwent standard total hysterectomy, bilateral salpingo-oophorectomy and omentectomy, and the majority had nodal staging. FIGO