Intermediate-Risk Prostate Cancer Treated With Hypofractionated External Beam Radiation Therapy Alone: Long-Term Outcomes

To report long-term tumor control and late gastrointestinal (GI) and genitourinary (GU) toxicity rates in intermediate-risk prostate cancer (IRPC) patients treated with high-dose hypofractionated radiation therapy (RT) alone. Between October 2002 and May 2010, 100 men with IRPC (T2b-T2c, prostate-specific antigen [PSA] 10-20ng/dL, or Gleason score [GS] 7) received hypofractionated external beam RT (EBRT) without androgen deprivation. The dose was 66 Gy in 22 daily fractions prescribed at the isocenter using 3-dimensional conformal technique. Daily image guidance of the prostate was performed by transabdominal ultrasound system. Planning target volume was defined as prostate (± 1-cm seminal vesicles) with 7-mm margin in all directions. There were no rectal or bladder constraints. Biochemical failure was defined according to Phoenix criteria (nadir + 2ng/dL). In general, follow-up was every 6 months during first 5 years and annually thereafter. GI and GU toxicity were prospectively assessed and scored according to the Common Terminology Criteria for Adverse Events version 3. Median follow-up was 75 months (range 7-143 months). Median age was 71 years (range 51-83 years); 65% had a Gleason score of 7. Median initial PSA was 8.67 ng/dL (range 1.1–18.6 ng/mL) and 42% had stage T2. Seven patients developed biochemical failure; 14 patients died, 2 from prostate cancer and 12 from other causes. Five- and 8-year actuarial biochemical recurrence-free, cancer-specific, and overall survival rates were 95% and 90%, 100% and 95%, and 89.5% and 85%, respectively. The worst grade 2-3 GU or GI late toxicity was 21% and 20%, respectively. At the last follow-up, grade 2-3 late GI and GU toxicity rates were 3% for both groups. No grade 4 or 5 late toxicity occurred. Hypofractionated EBRT using 66Gy in 22 fractions with 3-dimensional plan and without androgen deprivation is associated with excellent long-term biochemical control with acceptable late GU and GI toxicity. This is, to our knowledge, the longest reported follow-up in patients treated with high-dose hypofractionation alone. Our data cannot be extrapolated to the intensity modulated RT technique.