ESTRO 2023 - Abstract Book

S95

Saturday 13 May

ESTRO 2023

Results The DSCs (mean±standard deviation) for the 11 test cases were 0.93±0.05 (bladder), 0.85±0.08 (rectum), 0.79±0.10 (sigmoid), and 0.73±0.17 (small bowel) with the proposed loss function, which was similar to the baseline results (mean DSCs diff <0.02). The mean wDSCs were 0.98 and 0.98 for bladder, 0.93 and 0.92 for rectum, 0.91 and 0.89 for sigmoid, and 0.87 and 0.84 for small bowel in our proposed loss and baseline loss, respectively, indicating that our method has significant improvement in near-to-target region segmentation, especially for poorly predicted organs, like sigmoid and small bowel. Conclusion We have proposed a novel loss function for guiding the network to highly accurate proximal OARs segmentation. This subregion-aware loss function has shown promising results in improving the performance of near-to-target OAR regions and maintaining the whole organ segmentation performance, which addressed the real clinical needs of OAR contouring and will help to further generate optimized treatment plans. OC-0133 Dosimetric risk factors for vaginal and sexual toxicity in locally advanced cervix cancer A. Rink 1,2,3 , J. Hanuschak 4 , L. Conroy 1,2 , K. Han 4,2 , M. Milosevic 4,2 , J. Lukovic 4,2 , S. Ferguson 5 , A. Salman 5 , A. Santiago 6 , J.L. Conway 7,2 , J. Croke 4,2 1 University Health Network, Medical Physics, Toronto, Canada; 2 University of Toronto, Radiation Oncology, Toronto, Canada; 3 University of Toronto, Medical Biophysics, Toronto, Canada; 4 University Health Network, Radiation Medicine Program, Toronto, Canada; 5 University of Toronto, Gynecologic Oncology, Toronto, Canada; 6 University Health Network, Biostatistics, Toronto, Canada; 7 Royal Victoria Regional Health Centre, Radiation Oncology, Barrie, Canada Purpose or Objective HDR brachytherapy (BT) plays a critical role in the treatment of locally advanced cervical cancer. Our objective was to identify relationships between physician reported vaginal toxicity (VT) and patient reported sexual health outcomes (PROs) with dosimetric markers of HDR-BT in locally advanced cervix cancer. Materials and Methods This was a single-centre prospective cross-sectional study of Stage IB-IVA cervical cancer patients treated with definitive CRT and MR-guided BT who were disease-free for >3 months. Consenting patients completed validated PROs: Female Sexual Distress Scale-Revised (FSDS-R), Female Sexual Function Index (FSFI), and Menopause Rating Scale (MRS), as well as a socio- demographics questionnaire. Physicians prospectively scored VT using the CTCAE v4.0. Dosimetric markers are: equivalent dose in 2 Gy fractions (EQD2) for Vaginal D2cm and ICRU recto-vaginal (RV) point, maximum fractional Vaginal D2cc (MaxVagD2cc), maximum fractional point dose, MaxVagPoint, (among ICRU-RV and vaginal lateral points 5 mm from applicator), EQD2 for MaxVagPoint, maximum fractional vaginal total reference air kerma (TRAK), (MaxVagTRAK), and total vaginal TRAK (TotalVagTRAK). To explore associations with dosimetry, unadjusted univariate linear regression was performed for each variable as a function of PROs, physician assessed VT and clinical covariates. Results Between August 2018 and April 2022, 78 patients were enrolled and 74 completed PROs. Median age at diagnosis was 49.5 (range: 25-81), 51% were FIGO cT2b, and 61% had vaginal involvement at diagnosis. 76 patients received EBRT of 45Gy in 25 with/without simultaneous nodal boost or post-brachy nodal boost. 77 patients received 28Gy/4fx or 24Gy/3 fx HDR-BT. Median time from treatment was 19.8 months (3.3-57.1). Median HR-CTV D90 was 92.1Gy (81-106.4), ICRU-RV point was 61.8Gy (49.8-118.5) and vaginal D2cc was 76.8 Gy (54.7-133). Correlations between PROs, physician assessed VT and clinical data are summarized in Table 1. Dose to ICRU-RV and vaginal points were independently correlated with vaginal involvement at BT.