Phase II study of a four-week hypofractionated external beam radiotherapy regimen for prostate cancer: report on acute toxicity

Purpose: To evaluate the early side effects of a short course hypofractionated radiotherapy regimen in prostate cancer. Materials and methods: Three institutions (IRE, AZ VUB, GUH) included 36 patients with T1-T3N0M0 prostate cancer in a phase II study. Patients were treated with 56 Gy in 16 fractions over 4 weeks. Early side effects were scored using the RTOG/EORTC criteria and the international prostate symptom index (IPSI) weekly during treatment and 1 and 2 months afterwards. The results were compared with two control groups of patients previously treated with conventional fractionation at AZ VUB (238 patients) and GUH (114 patients). Results: None of the patients experienced grade 3-4 toxicity. Grade 1-2 Gastro-intestinal (GI), grade 2 GI, grade 1-2 Genito-urinary (GU) and grade 2 GU toxicity occurred in 75%, 36%, 75% and 44% for the hypofractionation schedule. The corresponding figures were 25-44%, 6-29%, 47-53% and 16-44% for the control groups (p < 0.01 for grade 1-2 GI and GU toxicity). Two months after treatment all GU and the majority of GI symptoms had resolved. The IPSI increased from (average ±1 SD) 5.6 ± 4 pre-treatment to 10.0 ± 6 during week 2-4 and had normalized (5.2 ± 4) two months after treatment. Conclusions: Though no grade 3-4 side effects were observed, the investigated schedule results in a marked increase of grade 1-2 early side effects as compared to a conventional regimen. Side effects resolved within two months post-treatment