Twice-weekly hypofractionated intensity-modulated radiotherapy for localized prostate cancer with low-risk nodal involvement: toxicity and outcome from a dose escalation pilot study.

To evaluate the toxicity and preliminary outcome of patients with localized prostate cancer treated with twice-weekly hypofractionated intensity-modulated radiotherapy (IMRT).Between 2003 and 2006, 82 prostate cancer patients with a nodal involvement risk ≤20% (Roach index) have been treated to the prostate with or without seminal vesicles with 56 Gy (4 Gy/fraction twice weekly) and an overall treatment time of 6.5 weeks. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were scored according to the Radiation Therapy Oncology Group (RTOG) grading system. Median follow-up was 48 months (range, 9-67 months).All patients completed the treatment without interruptions. No patient presented with Grade ≥3 acute GU or GI toxicity. Of the patients, 4% presented with Grade 2 GU or GI persistent acute toxicity 6 weeks after treatment completion. The estimated 4-year probability of Grade ≥2 late GU and GI toxicity-free survival were 94.2% ± 2.9% and 96.1% ± 2.2%, respectively. One patient presented with Grade 3 GI and another patient with Grade 4 GU late toxicity, which were transitory in both cases. The 4-year actuarial biochemical relapse-free survival was 91.3% ± 5.9%, 76.4% ± 8.8%, and 77.5% ± 8.9% for low-, intermediate-, and high-risk groups, respectively.In patients with localized prostate cancer, acute and late toxicity were minimal after dose-escalation administering twice-weekly 4 Gy to a total dose of 56 Gy, with IMRT. Further prospective trials are warranted to further assess the best fractionation schemes for these patients.