ESTRO 2023 - Abstract Book

S1919

Digital Posters

ESTRO 2023

- Day 2 - Wednesday: planning computed tomography (CT) and second IRT fraction delivery Second week

- Day 10 Thursday and Day 11 Friday: planning CT and third and fourth IRT fraction delivery The total IRT dose delivered to High Risk Tumor Volume was 28Gy (Total EQD2 dose > 90Gy). The CTCAE v. 5 scale was used to score the ≥ G3 late vaginal, gastrointestinal and genito-urinary late vaginal toxicity defined as any toxicity occurring six months after completion of HDR-IRT. Results Sixteen patients were analysed. Two, four and ten patients were Stage IIB, IIIA/B and IIIC1/2, respectively. The mean EQD2 for 0.1 cm3 of small bowel, rectum and bladder was 65.33Gy, 67.43Gy and 82.22Gy, respectively. The mean EQD2 for 0.2 cm3 of small bowel, rectum and bladder was 62.35Gy, 64.51Gy and 77.4Gy, respectively. The mean EQD2 for recto-vaginal point was 43.10 Gy. At a median follow-up of 14 months the loco-regional control, overall survival and cancer-specific survival were 90%, 97% and 100%, respectively. Late vaginal toxicity was recorded in 15 patients as follow: four, six and three stenosis G1, G2 and G3, respectively; nine, two and three atrophy G1, G2 and G3 respectively; seven and one teleangectasia G1 and G2, respectively. No ≥ G3 late gastrointestinal and genito-urinary toxicity was reported. Conclusion In the setting of concurrent chemo-radiotherapy, an accelerated IG-IRT treatment schedules seem to be feasible and safe in terms of late toxicity. Purpose or Objective Brachytherapy to bulky and asymmetrical cervical tumours is challenging even with combined intracavitary/interstitial (IC/IS) brachytherapy. Therefore, new brachytherapy applicator (Venezia) has been developed which allows the insertion of both parallel and oblique interstitial needles to improve dose coverage. Meanwhile, simpler method intracavitary brachytherapy with top-up IMRT boost was introduced by previous studies to treat advanced staged cervical cancer. Hence, the purpose of this study is to compare the dosimetric outcome between combined IC/IS brachytherapy and intracavitary brachytherapy with top-up IMRT in treating bulky and asymmetrical cervical tumours. Materials and Methods Five patients with cervical cancer of FIGO staged III or above treated by Venezia applicator were retrospectively recruited. The 4 brachytherapy fractions of each patients were re-planned by 2 treatment methods: combined IC/IS brachytherapy with parallel and oblique needles (IC/IS method) and intracavitary brachytherapy with top-up IMRT (IC/IM method). Analysis was made according to the summation of dose from external beam radiotherapy and brachytherapy, and the fractional dose of each brachytherapy session. Dosimetric comparison was carried out between the 2 planning methods in terms of dose delivered to the target volumes and dose sparing to OARs. The relationship between the tumour volume, weighting of IMRT used in IC/IM method and planning parameters was also analyzed by correlation test. Results The median dose that IC/IM method can further escalate from IC/IS method was 7.53 Gy to GTV D98, 6.86 Gy to HRCTV D98 and 6.54 Gy to IRCTV D98. The fractional dose from IC/IM method could delivered a significant higher dose to GTV D98, HRCTV D98 and IRCTV D98 than IC/IS method. However, the D2cc of sigmoid colon and small bowel were significantly higher for IC/IM method. The volume irradiated by low dose (V3.3) was also significantly higher for all OARs including bladder, rectum, sigmoid colon and small bowel for IC/IM method. The HRCTV volume was found to be significantly correlated with D98 of HRCTV and IRCTV, and V3.3 of all OARs. Meanwhile, the IMRT proportion in IC/IM method was only significantly correlated with the V3.3 of sigmoid colon. Conclusion The IC/IM method may allow further dose escalation to target volumes compared with IC/IS method. However, the dose sparing to OARs of IC/IM method was inferior to IC/IS method. Moreover, the top-up IMRT boost in IC/IM technique may suffer from uncertainties including intra-fractional deviation and setup error. Therefore, IC/IM technique should only be an alternative treatment approach when IC/IS technique was not able to deliver sufficient dose to target volumes. PO-2132 Dosimetric comparison between IC/IS brachytherapy and ICB with top-up IMRT for cervical cancer L.K. Lam 1 1 Pamela Youde Nethersole Eastern Hospital , Clinical oncology, Hong Kong, Hong Kong (SAR) China

PO-2133 MRI compatible tandem design for treatment of vaginal, cervical and endometrial brachytherapy

A. Beiki-ardakani 1 , I. Yeung 2 , A. Simeonov 2 , A. Rink 2 , J. Borg 2 , R. Weersink 2 , M. Milosevic 3 , J. Jezioranski 2

1 Princess Margaret Cancer Center, Radiation Physics, Toronto, Canada; 2 Princess Margaret Cancer Centre, Radiation Physics, Toronto, Canada; 3 Princess Margaret Cancer Centre, Radiation Oncology, Toronto, Canada Purpose or Objective MR-compatible applicators composed of plastic or titanium are available commercially for gynecological brachytherapy (BT). All current commercial tandems are closed end, can only be used for cervical cancer with an existing canal and cannot be used without available Ring or Venezia systems. Further, commercial tandems are prone to breaking in the patient during overnight stay. To overcome these issues, we introduce a biocompatible open and closed-ended brachytherapy tandem for the treatment of endometrial, cervical or vaginal cancer.

Materials and Methods