Urethral and bladder dosimetry and urinary toxicity in prostate cancer patients undergoing SBRT with and without intra-prostatic boost.

BACKGROUND AND PURPOSE

To evaluate the dosimetric and toxicity profiles of stereotactic body radiotherapy (SBRT) for prostate cancer, comparing cohorts with and without intraprostatic boost (IPB) to assess feasibility and safety of IPB, with particular attention to urethral and bladder dose and toxicity.

MATERIALS AND METHODS

This retrospective cohort study analyzed 349 patients with localized prostate cancer treated between 2018 and 2023. Of these, 266 received SBRT with IPB, and 83 received SBRT without IPB. Patients were treated using a robotic SBRT platform with fiducial tracking. Dosimetric parameters for the urethra, including D0.03cc, D0.3cc, and V40Gy, and for the bladder, including D0.03cc, D5cc, D10cc, and V37Gy, were evaluated. Acute and late toxicities were assessed using CTCAE criteria.

RESULTS

For the urethra, median values for D0.03cc, D0.3cc, and V40Gy, and for the bladder, median values D0.03cc, D5cc, D10cc, and V37Gy were compared and no statistically significant differences were observed between the two cohorts. Late urinary toxicity of grade 3 or higher occurred in 2.25 % of patients in the IPB group and 2.47 % in the no IPB group, with no grade 3 acute toxicities reported.

DISCUSSION

These findings support the use of SBRT using an IPB as a feasible and safe approach to achieve focal dose escalation to dominant intra-prostatic lesions (DILs) without significantly increasing urethra or bladder dose or toxicity. Future research should focus on standardizing DIL contouring, exploring adaptive planning techniques to increase accuracy, and prospectively studying toxicity and quality of life in patients treated with IPB with SBRT.