Introduction/Background Obesity, a risk factor for endometrial cancer (EC), complicates radiotherapy due to technical constraints and increased acute toxicity. Our study explores weight's impact on postoperative radiotherapy (PORT) toxicities in women treated for EC.

Methodology in a retrospective study, we report 30 cases of EC, treated with PORT at Farhat Hached university hospital's radiotherapy department in Sousse, Tunisia between 2013 and 2021. Acute toxicities related to PORT were classified according to the CTCAE scale (common terminology of criteria for adverse events)V5.0. Body mass index (BMI) was classified using WHO criteria.

Results The average weight was 78.16 Kg [57–110 Kg]. The average BMI was 28.48 Kg/m2 [19.7–41.4 Kg/m2] . The patients were classified according to the BMI in: normal weight [BMI< 25Kg/m2] (30%), overweight [BMI 25–30Kg/m2] (30%), obesity [BMI 30–40 Kg/m2] (36%) and morbid obesity [BMI> 40Kg/m2] (4%).

All patients underwent 3D conformational PORT targeting the whole pelvic and vaginal cuff, with a median dose of 45 Gy [45–50.4] delivered at 1.8 Gy/session, five sessions/week. The energies delivered were 6 and 18 MV. Sixty percent received concurrent or adjuvant chemotherapy (61% and 39%), and all patients underwent high dose rate brachytherapy up to a total dose of 60 Gy.

Acute gastrointestinal toxicities such as diarrhea were frequently reported (60%) with 50% Grade II toxicity.Grade III toxicity (20%) was predominantly observed in patients with lombo-aortic irradiation, concurrent chemotherapy, and BMI over 30 kg/m2 (7%). Radiodermatitis-type skin toxicities occurred in 70%, mostly Grade II (57%). Grade III skin toxicities were noted in 23%, exclusively in patients with a BMI exceeding 30 kg/m2. Genitourinary (GU) toxicities were reported in 40%, mainly in obese women with a BMI greater than 30 kg/m2.

Conclusion Obesity influences tolerance to PORT in EC. However, systematic weight loss programs for oncological therapeutic purposes should be recommended for this population of obese women.

Disclosures All authors declare that they have no conflicts of interest.