ESTRO 2024 - Abstract Book

S2560

Clinical - Urology

ESTRO 2024

The management of locally recurrent prostate cancer presents a considerable clinical challenge necessitating innovative treatment paradigms. Biology-guided radiotherapy (BgRT) employs tumor emissions following a radiotracer injection as a dynamic guide for real-time refinement of the radiotherapeutic beamlet. This study assesses the dosimetric feasibility of 18F-Choline and 68Ga-PSMA -guided BgRT in terms of target coverage and dose reduction to the bladder and rectal walls for patients with prostatic bed recurrences.

Material/Methods:

In this retrospective study, data from 15 patients with locally recurrent prostate cancer who underwent 18F-Choline or 68Ga-PSMA PET/CT imaging were included. The gross tumor volume (GTV) was delineated based on the PET images, and an 8 mm clinical target volume margin was defined. For BgRT planning, an expansion of 3 mm for planning target volume (PTV) and 5 mm for biology tracking zone (BTZ), respectively, was applied. BgRT plans with a prescription dose of 36 Gy/6 fractions were generated using a research version of the RefleXion® X1 TPS. The dose distribution to the bladder and rectal walls was analyzed.

Results:

BgRT plans were successfully created for the 15 patients, with PTV volumes ranging from 15.74 to 168.98 cc. The plan aimed to reduce radiation exposure to critical organs while maintaining adequate target coverage. In most cases, the bladder and rectum overlapped with the PTV. Mean doses to the bladder and rectal walls were 12.65±4.71 Gy (range: 4.24 - 19.82 Gy) and 14.37±3.17 Gy (range: 4.03 - 19.71 Gy), respectively.The V12Gy values for the bladder and rectum walls ranged from 12.6% to 76.9% and 11.6% to 72.6%, respectively.

Conclusion:

This study demonstrates the dosimetric evaluation of BgRT planning for locally recurrent prostate cancer patients with 18F-Choline or 68Ga-PSMA PET avidity. It highlights the potential of 18F-Choline and 68Ga-PSMA PET as both a diagnostic tool and a means to guide radiation therapy, offering a promising approach to treat prostate bed relapses. Further analysis is warranted to address deliverability of 18F-Choline and 68Ga-PSMA PET/CT BgRT plans.

Keywords: BgRT, Recurrent prostate cancer, PET scan

2651

Digital Poster

Preliminary clinical outcomes of adaptive prostate SBRT using a conventional linac

Jose Torices, Juan Francisco Calvo, Coral Laosa, Sandra Moragues, Enrique Puertas

Hospital Quironsalud Barcelona, Radiation Oncology, Barcelona, Spain

Purpose/Objective: