ESTRO 2023 - Abstract Book

S1232

Digital Posters

ESTRO 2023

Materials and Methods During 2017 to 2020, 34 prostate cancer patients, planned for combined high dose rate brachytherapy (14,5 Gy x 1) and external beam RT (3 Gy x 14) were included in a randomized trial to receive treatment either three or five times per week. External RT was delivered utilizing small margins (3 mm) using the Raypilot system for real-time tracking of intrafractional prostate movements. Movements were continuously monitored in three dimensions during a total of 399 fractions. The beam was turned off if a displacement exceeded 2 mm for more than four seconds and patients were repositioned if the displacement persisted for 30 seconds. Toxicity was primarily assessed using patient-reported outcome measures through EORTC QLQ-C30 and QLQ-PR25. Results In total, 34 patients (17 in each study arm) were included in the study (median age was 70 years). For the entire study cohort, the average urinary symptoms score increased from 18.2 to 32.6 (p = 0.003) and the average global health status score decreased from 79.2 to 67.5 (p = 0.04) during the first 12 months of follow-up. No statistically significant long-term differences in toxicity between the two delivery schemes were observed (Fig 1).

Transmitter displacement was less than 2 mm during 97.0% of the time and less than 3 mm during 99.9% of the time (Fig 2). A displacement exceeding 2 mm in any dimension for at least 4 seconds was seen in 42 (11 %) fractions. The most common event was a negative vertical displacement (transmitter displaced towards the back of the patient). Patients having the transmitter located near the base of the prostate, had no treatment interruptions. Patients who had the transmitter placed centrally or near the apex had an average of 2.9 and 1.5 treatment interruptions per fraction, respectively.

Conclusion Small margins when using a real-time tracking system are feasible and might facilitate more frequent dose delivery schemes. Provided that the CTV is properly delineated, and the transmitter approximately centrally located, a 3 mm margin can be considered safe when using a real-time tracking system with only a limited part of the radiation to be delivered when the target is displaced more than 2 mm.

PO-1516 Quality of Life After Radical Treatment for Bladder Cancer – lived experience of patients & carers.

S. Appleyard 1 , N. Wietek 2 , C. Moynihan 3 , A. Nikapota 1 , A. Robinson 1 , C. Manetta 1 , R. Huddart 4