Stages I–III Inoperable Endometrial Carcinoma: A Retrospective Analysis by the Gynaecological Cancer GEC-ESTRO Working Group of Patients Treated with External Beam Irradiation and 3D-Image Guided Brachytherapy †

SIMPLE SUMMARY: About 10% of early-stage endometrial cancers (EC) are inoperable. Curative treatment is still recommended in these cases. The aim of this retrospective study, which is the largest in the literature, was to analyse the outcomes of stages I–III EC patients treated with the intention to cure by external beam irradiation (EBRT) and 3D-image-guided brachytherapy (IGBT). EBRT+IGBT provides good cancer-specific survival results of 88.7% and 71.2% at 2 and 5 years, respectively. A few patients without uterine relapses developed nodal or systemic relapses, highlighting the importance of uterine control. ABSTRACT: Background/Purpose: Analyse the outcomes of stages I–III inoperable endometrial cancer (IEC) patients treated with external-beam-irradiation (EBRT) and 3D-image-guided-brachytherapy (IGBT). Material and Methods: Medical records of IEC patients receiving EBRT + IGBT in eight European and one Canadian centres (2004–2019) were examined, including: pelvic ± para-aortic EBRT and lymph node boost; anaesthetic procedure, applicators, BT-planning imaging, clinical target volume (CTV), brachytherapy schedule, and EQD2 to the CTV((α/β=4.5Gy)) and D2 cm(3)((α/β=3Gy)) for organs at risk. Complications are evaluated using CTCAEv4 scores. The 2- and 5-year survival probability according to stages was estimated (cancer-specific survival (CSS), disease-free survival (DFS), local relapse-free survival (LRFS), loco-regional relapse-free survival (LRRFS), and distant metastasis-free survival (DMFS)). Statistics: descriptive analysis and the Kaplan–Meier method. Results: 103 patients (stages: I-44, II-14, III-44) were included. Median follow-up: 28 months (7–170). All patients received pelvic ± para-aortic EBRT. Median D90-EQD2((α/β=4.5)) to the CTV:73.3 Gy (44.6–132.7), 69.9 Gy (44.7–87.9 and 75.2 Gy (55.1–97) in stages I, II, and III, respectively. Thirty patients presented relapse (stages: 10-I, 3-II, 17-III): 24 uterine (stages: 7-I, 3-II, 14-III), 15 nodal (stages: 4-I, 1-II, 10-III), and 23 distant (stages: 6-I, 2-II, 15-III). Five year CSS was 71.2% (stages: 82%-I-II and 56%-III) and DFS, LRFS, LRRFS, and DMFS were 55.5%, 59%, 72%, and 67.2%, respectively. Late G3-G4 complications (crude): 1.3% small bowel, 2.5% rectum, and 5% bladder. Conclusion: In stages I–III of the IEC, EBRT + IGBT offer good 2- and 5-year CSS of 88.7% and 71.2%, respectively, with the best outcomes in stages I–II. Prospective studies are needed to determine how better outcomes can be achieved.