Hypofractionated Conformal Radiotherapy for Good Prognosis Carcinoma of the Prostate: Seven Year Outcome Analysis

Abstract

The optimal external beam radiotherapy dose and fractionation in the radical treatment of localised prostate cancer continues to be investigated. This includes not only dose escalation using conventional fractionation, but also the exploration of hypo-fractionated regimes for prostate cancer given its suggested low α/β ratio. We report the long term efficacy of radiotherapy using a hypo-fractionated 50 Gy in 16 fractions (3.13 Gy per fraction) in men with localised prostate cancer. A retrospective review of men with localised prostate cancer treated consecutively with conformal radiotherapy at a single institution between January 1995 and May 2001 was performed. Only patient's in the good prognostic group (PSA ≤10 ng/ml and Gleason score ≤6 and clinical stage T1/2) were included in the study. A conformal external beam radiotherapy dose of 50 Gy in 16 fractions over 22 days was delivered using a 4 field arrangement on a linear accelerator with energy ≥6 MV. The planning target volume (PTV) was defined as GTV (Prostate ± base of seminal vesicles) + 1 cm in all directions except posteriorly where 7 mm was used. Patients treated with neo-adjuvant, concurrent or adjuvant hormonal therapies were excluded. Biochemical failure was defined using both the American Society for Therapeutic Radiology and Oncology consensus definition and Phoenix definition. One hundred and ninety nine men were identified. 73 with clinical T1 and 126 with clinical T2 disease at presentation. The median age at presentation was 67.9 years (49.9–81.65 years) and median initial PSA was 5.9 ng/ml (0.1–10 ng/ml). Histological review demonstrated that 78, 49 and 72 patients had Gleason scores of ≤4, 5 and 6 respectively. At a median follow-up of 84 months (4.6–134.9 months), the 7 year actuarial overall survival was 83.2% and the biochemical failure free survival was 55% and 76.8% as defined by the ASTRO consensus and Phoenix definition respectively. This data demonstrates the efficacy of a hypo-fractionated regime for good prognosis patients. It provides similar levels of biochemical control when compared with other reported long term outcomes using conventionally fractionated radiotherapy (2 Gy per fraction).