ESTRO 2020 Abstract Book

S1099 ESTRO 2020

workshop surveys and were available for analysis. Of resident attendees, 60% reported attending the station utilizing virtual reality to teach US-guidance and 60% attended the station utilizing an US-compatible mannequin. Of non-residents, 53% attended an US station. Overall, the majority of session attendees reported increased comfort with US-guidance following the workshop (65%). Amongst residents attending an US station, 78% reported increased comfort with US-guidance. Conclusion This study demonstrated the feasibility of implementing a national SBE gynecological BT session utilizing high fidelity US-compatible simulators. Self-reported measures of procedural comfort suggested efficacy of the workshop but more objective measures of workshop efficacy are needed. Future work should also focus on increasing opportunities for SBE workshops, at both BT and non-BT RO meetings, as well as increasing the availability and affordability of US- compatible simulators. OC-1049 Dose-effect relationship between vaginal dose points and vaginal stenosis in cervical cancer H. Westerveld 1 , K. Kirchheiner 2 , R.A. Nout 3 , K. Tanderup 4 , J.C. Lindegaard 4 , S. Spampinato 4 , A. Sturdza 2 , N. Nesvacil 2 , K. Bruheim 5 , T.P. Hellebust 5 , B.R. Pieters 1 , I.M. Jürgenliemk-Schulz 6 , R. Pötter 2 , A. De Leeuw 6 1 Amsterdam University Medical Centers- Academic Medical Center, Radiation Oncology, Amsterdam, The Netherlands ; 2 Comprehensive Cancer Center- Medical University of Vienna / General Hospital of Vienna, Radiation Oncology, Vienna, Austria ; 3 Erasmus MC Cancer Institute- Erasmus University Medical Center, Radiation Oncology, Rotterdam, The Netherlands ; 4 Aarhus University Hospital, Oncology, Aarhus, Denmark ; 5 The Radium Hospital- Oslo University Hospital, Oncology, Oslo, Norway ; 6 University Medical Centre Utrecht, Radiation Oncology, Utrecht, The Netherlands Purpose or Objective To evaluate the dose-effect relationship between vaginal dose points and vaginal stenosis in patients treated within the prospective, observational, multi-center EMBRACE study (an IntErnational study on MRI-guided BRAchytherapy in locally advanced CErvical cancer). Material and Methods For this EMBRACE sub-study 304 out of 1416 patients from six centers were included (treatment period 2008-2015). All patients were treated with combined EBRT ± chemotherapy and image-guided adaptive brachytherapy (IGABT) following the GEC-ESTRO recommendations. Information about the doses to the Posterior–Inferior Border of Symphysis (PIBS), PIBS+2 and PIBS-2 points, representing the mid and lower part of the vagina were retrospectively retrieved from the treatment planning system. In addition, the vaginal reference length (VRL) and the dose to the recto-vaginal reference point (RVRP), representing the dose in the upper vagina (high-dose region) were evaluated (Figure 1). Vaginal stenosis was prospectively assessed according to the CTCAEv3.0 scoring system at baseline and follow-up every 3 months (1 st year), every 6 months (2 nd ,3 rd year) and yearly thereafter. Grade 2 or higher (G≥2) vaginal stenosis was considered a clinically relevant endpoint as it represents vaginal narrowing and/or shortening interfering with function. Patients followed institutional sexual rehab programs and protocols for the use of hormones. Impact of dose to the PIBS and RVRP points, and impact of VRL, age and vaginal involvement on vaginal stenosis G≥2 was evaluated with a univariate Cox proportional hazard regression model.

Results Median age was 47 years. Median follow-up was 49 months. FIGO-stage distribution was as following: stage I 63 (21%), II 179 (59%), III 34 (11%), and IV 27 (9%). At diagnosis, 177 (58%), 110 (36%) and 17 (6%) patients had no, upper third or middle/lower third vaginal involvement, respectively. During follow-up, 77 (25%), 160 (53%), 59 (19%) and 8 (3%) had G0, G1, G2 and G3 vaginal stenosis, respectively. Median vaginal reference length (VRL) was 54 mm (interquartile range (IQR) 43-64 mm). Median doses to PIBS+2, PIBS, PIBS-2 and the RVRP were 52.9 (IQR 49.2- 64.3), 41.2 (IQR 15.8-49.1), 4.1 (IQR 2.9-7.0) and 64.6 (IQR 60.0-70.6) Gy, respectively. Higher doses to the PIBS, PIBS+2, PIBS-2 point, and the RVRP were significantly associated with higher risk for vaginal stenosis G≥2 (Figure 2). Further univariate risk factors for vaginal stenosis were a shorter VRL, higher age and vaginal involvement at diagnosis.

Conclusion Vaginal stenosis ≥G2 is significantly associated with higher doses to the PIBS points, representing the lower parts of the vagina. In addition, this report confirms the earlier described dose-effect relationship between vaginal