Exclusive 3D-brachytherapy as a good option for stage-I inoperable endometrial cancer: a retrospective analysis in the gynaecological cancer GEC-ESTRO Working Group

Purpose: Analyse outcomes of stage-I inoperable endometrial cancer (EC) patients from seven European centres treated with 3D-image-guided brachytherapy (IGBT) alone.

Materials and methods: From 2004 to 2018, 62 patients (41 stage-IA and 21 IB) were retrospectively studied, analysing anaesthetic procedure, applicator type, BT-planning imaging, clinical target volume (CTV), BT schedule, overall daily-dose equivalent to 2 Gy (EQD2_{(α/β=4.5 or 3)}) to the CTV_(α/β=4.5) and D2 cm³_(α/β=3) for organs at risk. Complications were evaluated using CTCAEv4 scores. The 2 and 5 year survival was calculated [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)]. Descriptive analysis and the Kaplan-Meier method were used for survival analysis.

Results: Mean follow-up: 32.8 months (SD 33.7). Spinal anaesthesia (38/62) followed by none (16/62) were the most common. Y-shaped Rotte applicators were used in 74% of patients. High-dose rate brachytherapy was administered in 89%. Median D90 to the CTV was 58.9 Gy (8.66-144 Gy). Eight patients presented relapse: four uterine, four nodal and four distant. The 2 and 5 year CSS was 93.3 and 80.5%, DFS 84.8 and 80.5%, LRFS was 93.1 and 88.7%, LRRFS was 91 and 91% and DMFS was 90.2 and 90.2%, respectively, CSS was better in stage-IA vs. IB (p = 0.043). Late vaginal and bladder G3-complication rates were 2.1%, respectively.

Conclusion: Inoperable EC patients can be safely treated by BT with 2 and 5 year CSS of 93 and 80.5%, respectively, with even better results for IA cases. Prospective studies on 3D-IGBT are necessary to better analyse EC patient outcomes based on dose and treated volumes.