ESTRO 2023 - Abstract Book

S1240

Digital Posters

ESTRO 2023

The example of HDRB and SBRT boost doses are shown in Figure 1. The main limiting constraint in SBRT is dose on the urethra. On the contrary to brachytherapy where urethra is fixed, in SBRT urethra PRV has to be defined even though prostate is tracked with fiducial markers. Few patients are already being treated according to the presented protocol.

Fig 1: Example of HDRB and SBRT dose distributions

Conclusion We demonstrated that it is possible to achieve SBRT boost plans of escalated dose to the dominant intraprostatic lesion while maintaining acceptable urethral dose. This technique is suitable for patients that undergo EBRT but due to medical conditions (long COVID, acute myocardial infarction…) cannot receive scheduled HDRB boost. When prior to EBRT is known that patient is not suitable for brachytherapy, other regimes of external irradiation (60Gy/20fx, 42.7Gy/7fx) are used.

PO-1525 Evaluation of novel dose-volume constraints in patients treated with EBRT for local prostate cancer

N. O'Sullivan 1 , C. Lyons 2

1 Cork University Hospital, Radiation Oncology, Cork, Ireland; 2 Cork Univeristy Hospital, Radiation Oncology, Cork, Ireland

Purpose or Objective The CHHiP trial demonstrated that 60Gy/20# was non-inferior to conventionally fractionationated schedules. Bowel side effects were observed in 13.7%. Recently, Wilkins et al. identified novel dose-volume constraints (DVCs) derived from CHHiP with the goal of reducing anorectal toxicity. Patients treated with 60Gy/20# were reviewed to investigate whether these DVCs were met and whether a similar reduction in gastrointestinal toxicity was observed. Materials and Methods All patients treated by a single clinician who completed 60Gy/20# between 01/01/2022 and 31/12/2020 were included. An electronic chart review was conducted using Mosaiq™. Data assessed included total duration of treatment, delays, re-plans, iPSA, Gleason score, TNM staging, and role of hormone therapy. Clinician-reported outcomes and patient-reported outcome measures (PROMs) EPIC and IPSS were collected prior to treatment and at 4/52, 4/12, 8/12, and 1 year. The DVCs examined were V24.6<80%, V32.4<70%, V40.8<60%, V52.8<30%, V60<3% versus V20<85%, V30<57%, V40<38%, V50<22%, V60<0.01%. Results 66 patients were treated during this time. Compliance with PROMs was inconsistent. Moderate gastrointestinal side effects were observed in patients, peaking 4 weeks post-treatment. Clinician-reported outcomes were reported in 42.4% of patients while on treatment. CHHiP DVCs were met in 95.46%. All novel DVCs were not met in any patient. However, between 30 100% were found to be within 3% depending on specific DVC. Conclusion Novel anorectal DVCs derived from the CHHiP trial were not fully met in any patient. No significant differences were observed in gastrointestinal toxicities compared to available literature, however a reduction in gastrointestinal toxicites were observed among patients who were <3% from achieving novel DVCs compared to those who were >3% from novel DVCs. These novel DVCs will be incorporated into the next revision of the prostate radiotherapy protocol.

PO-1526 Hypo-fractionated radiotherapy in elderly bladder cancer patients unfit for trimodal therapy.

F. Kraja 1 , A. Janko 2 , A. Hoti 3 , E. Tole 4 , E. Karaulli 1 , R. Xhani 2 , E. Hoxha 2 , B. Kreka 1