ESTRO 2021 Abstract Book

S205

ESTRO 2021

Conclusion IMRT resulted in significant lower rates of grade >2 diarrhoea and haematological AE during follow-up. Trends towards less patient-reported diarrhoea, bowel urgency and abdominal cramps were observed after IMRT compared to 3DCRT. IMRT/VMAT should be the standard techniques for women receiving adjuvant radiotherapy for high-risk endometrial cancer. OC-0299 Is pelvic radiation the right approach after surgery for FIGO IB grade 3 or type II uterine cancers? Z. Horne 1 , M. Manire 2 , S. Crafton 3 , E. Miller 3 , J. Nakayama 3 , C. Morse 3 , T. Krivak 3 , S. Glaser 4 , S. Teterichko 5 , S. Beriwal 6 1 Allegheny Health Network Cancer Institute, Radiation Oncology, Pittsburgh, USA; 2 West Penn Hospital, Obstetrics and Gynecology, Pittsburgh, USA; 3 Allegheny Health Network Cancer Institute, Gynecologic Oncology, Pittsburgh, USA; 4 City of Hope National Medical Center, Radiation Oncology, Duarte, USA; 5 University of Pittsburgh Medical Center, Obstetrics and Gynecology, Pittsburgh, USA; 6 Hillman Cancer Center, Radiation Oncology, Pittsburgh, USA Purpose or Objective The Post-Operative Radiation Therapy in Endometrial Cancer (PORTEC) 1 trial excluded randomization of women with FIGO 1B (previous FIGO IC) grade 3 endometrioid adenocarcinoma and instead delivered adjuvant pelvic external beam radiation therapy (EBRT) on a prospective protocol. Current National Comprehensive Cancer Network recommendations are for pelvic external beam radiation with chemotherapy being a category 2B recommendation. Gynecologic Oncology Group study 249 failed to show a survival advantage utilizing chemotherapy and vaginal brachytherapy (VBT) over EBRT in a population that included women with FIGO IB grade 3 endometrioid adenocarcinomas and FIGO stage I clear cell/serous carcinomas. We conducted an analysis of patterns of care and outcomes in his early-stage, high-risk population in the United States. Materials and Methods The National Cancer Data Base was queried for women with surgically staged, non-metastatic FIGO 2018 IB grade 3 endometrioid, papillary serous or clear cell uterine cancers between 2004 and 2016. Bivariate univariable and multivariable regression analyses determined treatment associations. Kaplan-Meier with log- rank test and Cox multivariable hazards test were used to determine overall survival. Results A total of 7,680 women were identified who met criteria. Of those women, 2,531 (33.0%) received no adjuvant treatment, 2,035 (26.5%) received EBRT alone, 1,249 (16.3%) received VBT alone, 564 (7.3%) received EBRT + chemotherapy, 746 (9.7%) received VBT + chemo, and 555 (7.2%) received chemotherapy alone. Median survival after NFT was 97.4 months, 131.8 months after EBRT, 128.6 after VBT, 124.2 after EBRT + chemo, 147.4 after VBT + chemo, and 108.3 after chemo alone (p<0.001). On multivariable analysis, age (HR 1.052 [95%CI 1.140-1.554], p<0.001), African American race (HR 1.430 [95%CI 1.195-1.711], p<0.001), comorbidity score >1 (HR 1.372 [95%CI 1.092-1.725], p=0.007), surgical nodal evaluation (HR 0.669 [95%CI 0.578-0.774], p<0.001), lymphovascular space invasion (HR 1.507 [95%CI 1.338- 1.697], p<0.001), adjuvant EBRT/VBT (HR 0.785 [95%CI 0.684-0.901], p=0.001), and adjuvant EBRT/VBT + chemotherapy (HR 0.691 [95%CI 0.579-0.825], p<0.001) were all significant for overall survival. Adjuvant EBRT/VBT + chemotherapy was significant for overall survival in comparison to adjuvant EBRT alone (HR 0.819 [95%CI 0.662-0.923], p=0.04).