Moderate hypofractionated external beam radiotherapy alone for intermediate risk prostate cancer: long term outcomes.

Introduction: To report long term toxicity and efficacy of patients with intermediate risk prostate cancer treated with moderate hypofractionated radiotherapy (HypoRT).

Materials And Methods: We studied the first consecutive 100 men with intermediate risk (stage T2b-T2c, or PSA = 10-20 ug/L, or Gleason score = 7) adenocarcinoma of the prostate treated between October 2002 and May 2010 in our institution with moderate HypoRT. Patients were treated using three-dimensional conformal HypoRT to a dose of 66 Gy in 22 daily fractions prescribed to the isocenter. Androgen suppression was not given to any patient. A uniform 7 mm margin was created around the prostate for the planning target volume. Daily ultrasound was used to guide the radiotherapy. Common Terminology Criteria for Adverse Events, version 3.0, was used to prospectively score toxicity. Biochemical failure was defined as the nadir PSA level plus 2 ng/m.

Results: After a median follow up time of 80 months (range: 7-152), the 8 year actuarial freedom from biochemical relapse survival rate was 90%. The 8 year cancer specific survival and overall survival rates were 96% and 84%, respectively. Only 2 patients died from prostate cancer. The worst grade ≥ 2 late genitourinary (GU) or gastrointestinal (GI) toxicities ever documented were 19% and 20%, respectively. At the last follow up the incidence of grade ≥ 2 late GI or GU toxicity was of only 2% and 3%, respectively. No grade 4 or 5 late toxicity was seen.

Conclusion: Our long term experience with HypoRT delivering 66 Gy/22 fractions prescribed to the isocenter using three-dimensional conformal radiotherapy shows excellent tumor control with acceptable toxicity.