Hypofractionated helical intensity-modulated radiotherapy (75 Gy at 2.5 Gy/fraction) for intermediate- and high-risk prostate cancer: Assessment of toxicity

Purpose: To evaluate the toxicity of hypofractionated helical intensity-modulated radiotherapy (IMRT) for men with intermediate- and high-risk prostate cancer. Methods and Materials: A retrospective toxicity analysis was performed in 22 patients treated definitively with hypofractionated helical IMRT. The helical IMRT were designed to deliver 75 Gy in 2.5 Gy/fraction to the prostate gland, 63 Gy in 2.1 Gy/fraction to seminal vesicle, and 54 Gy in 1.8 Gy/fraction to pelvic lymph nodes. No patient received hormonal therapy. Toxicity was graded by the Radiation Therapy Oncology Group (RTOG) scales. Results: All patients tolerated the treatment well without treatment interruption, and there was no Grade 3 or more acute toxicity. With a median follow-up of 24.5 months, there was no Grade 3 or more late toxicity. The late Grade 2 gastrointestinal (GI) and genitourinary (GU) toxicity for total 22 patients were 9.1% and 18.2%, respectively, and the late Grade 1 GI and GU toxicity were 18.2% and 50%, respectively. Late GU toxicity was associated with greater bladder volume irradiated ≥70 Gy. Late GI toxicity did not correlate with any of the dosimetric parameters. Conclusions: This study demonstrate that hypofractionated helical IMRT with high biologic effective dose (BED) is well tolerated with favourable toxicity rate. If longer follow-up periods and larger cohorts confirm the favourable biochemical control rate and our favourable toxicity assessment results, the hypofractionated IMRT (total 75 Gy, 2.5 Gy/fraction) might be implemented in clinical field for treatment of prostate cancer.