Comparison of Late Urinary Symptoms Following SBRT and SBRT with IMRT Supplementation for Prostate Cancer.

Background: Prostate cancer survivors commonly experience late-onset lower urinary tract symptoms following radiotherapy. We aimed to compare lower urinary tract symptoms in patients treated with stereotactic body radiotherapy (SBRT) to those treated with a combination of lower dose SBRT and supplemental intensity-modulated radiotherapy (SBRT + IMRT).

Methods: Subjects with localized prostate carcinoma scheduled to receive SBRT or a combination of SBRT and IMRT were enrolled and followed for up to 2 years after treatment completion. Participants treated with SBRT received 35-36.25 Gy in 5 fractions, while those treated with SBRT + IMRT received 19.5 Gy of SBRT in 3 fractions followed by 45-50.4 Gy of IMRT in 25-28 fractions. Urinary symptoms were measured using the American Urological Association (AUA) Symptom Score.

Results: Two hundred patients received SBRT (52% intermediate risk, 37.5% low risk according to D'Amico classification) and 145 patients received SBRT + IMRT (61.4% high risk, 35.2% intermediate risk). Both groups experienced a transient spike in urinary symptoms 1 month after treatment. More severe late urinary flare (increase in AUA scores ≥ 5 points from baseline to 1 year after treatment completion and an AUA score ≥ 15 at 1 year after treatment) was experienced by patients who received SBRT compared to those treated with SBRT + IMRT.

Conclusion: Participants who received SBRT and supplemental IMRT experienced less severe late urinary flare 1 year after treatment compared to those who received higher dose SBRT alone. This information can be used by clinicians to provide patients with anticipatory counseling to mitigate any psychological burden that comes with unanticipated late urinary toxicities.