Ultrahypofractionated linac-based radiotherapy of primary prostate cancer - early results of an Austrian nationwide registry study.

Ultrahypofractionated radiotherapy (UHFX) has emerged as an attractive alternative to normo- and moderately hypofractionated regimens for localized prostate cancer.

However, its broader adoption remains limited by technical challenges and concerns regarding genitourinary toxicity. We established a nationwide Austrian registry of low and intermediate risk localized prostate cancer patients treated with linac-based stereotactic body radiation therapy (SBRT) to provide real-world data about UHFX treatment conventions, toxicity, oncologic outcomes, and patient-reported quality of life (QoL). This is a multicenter, registry-based prospective study. Eligibility was restricted to patients with low- and intermediate-risk prostate cancer.

Patient characteristics, toxicity (CTCAE v5.1), urinary function (IPSS), and QoL (EPIC-26) were prospectively reported in a web-based database. Between September 2022 and April 2026, 191 patients were enrolled, of whom 169 were included in the final analysis. Median follow-up was 14 months (IQR 7-24). NCCN risk distribution consisted of 23.7% low-risk, 48.5% favorable intermediate-risk, and 27.8% unfavorable intermediate-risk disease.

All patients received 40 Gy in five fractions. Treatment was delivered on alternating weekdays in 61.5% and on consecutive weekdays in 38.5% of patients. Median PSA declined from 7.74 ng/mL at baseline to 0.63 ng/mL at 12 months. No biochemical recurrence was observed during the first year of follow-up.

Grade 1-2 genitourinary toxicity peaked at treatment completion and declined thereafter, while grade ≥ 3 toxicity remained uncommon (