Acute side effects after definitive stereotactic body radiation therapy (SBRT) for patients with clinically localized prostate cancer. A single institution prospective study.

Abstract

Purpose: To evaluate acute side effects after extremely hypofractionated intensity-modulated radiotherapy (IMRT) with stereotactic body radiation therapy (SBRT) for definitive treatment of prostate cancer patients.

Patients and methods: Between February 2018 and August 2018, 205 low-, intermediate- and high-risk prostate cancer patients were treated with SBRT using "CyberKnife M6" linear accelerator. In low-risk patients 7.5-8 Gy was delivered to the prostate gland by each fraction. For intermediate- and high-risk disease a dose of 7.5-8 Gy was delivered to the prostate and 6-6.5 Gy to the seminal vesicles by each fraction with a simultaneous integrated boost (SIB) technique. A total of 5 fractions (total dose 37.5-40 Gy) were given on every second working days. Acute radiogenic genitourinary (GU) and gastrointestinal (GI) side effects were assessed using RTOG scoring system.

Results: Of the 205 patients (28 low-, 115 intermediate-, 62 high-risk) treated with SBRT, 203 (99%) completed the radiotherapy as planned. The duration of radiation therapy was 1 week and 3 days. The frequency of acute radiogenic side effects were as follows: GU grade 0: 17.1%, grade I: 30.7%, grade II: 50.7%, grade III: 1.5% and GI grade 0: 62.4%, grade I: 31.7%, grade II: 5.9%, grade III: 0%. None of the patients developed grade ≥4 acute toxicity.

Conclusion: SBRT with a total dose of 37.5-40 Gy in 5 fractions appears to be a safe and well tolerated treatment option in patients with prostate cancer, associated with moderate or slight early side effects. Longer follow-up is needed to evaluate long-term toxicity and biochemical control.

Keywords: prostate cancer, stereotactic radiotherapy, CyberKnife, extreme hypofractionation