Stereotactic hypofractionated accurate radiotherapy of the prostate (SHARP), 33.5 Gy in five fractions for localized disease: First clinical trial results.

Berit L. Madsen. IJROBP 2007;67:1099

To evaluate the feasibility and toxicity of stereotactic hypofractionated accurate radiotherapy (SHARP) for localized prostate cancer.A Phase I/II trial of SHARP performed for localized prostate cancer using 33.5 Gy in 5 fractions, calculated to be biologically equivalent to 78 Gy in 2 Gy fractions (α/β ratio of 1.5 Gy).

The study includes 40 patients. The median follow-up is 41 months (range, 2160 months). Acute toxicity Grade 12 was 48.5% (GU) and 39% (GI); 1 acute Grade 3 GU toxicity. Late Grade 12 toxicity was 45% (GU) and 37% (GI). No late Grade 3 or higher toxicity was reported. Twenty-six patients reported potency before therapy; 6 (23%) have developed impotence. Median time to PSA nadir was 18 months with the majority of nadirs less than 1.0 ng/mL.

The actuarial 48-month biochemical freedom from relapse is 70% for the American Society for Therapeutic Radiology and Oncology definition and 90% by the alternative nadir + 2 ng/mL failure definition. Conclusions: SHARP for localized prostate cancer is feasible with minimal acute or late toxicity. Dose escalation should be possible. Patients enrolled in the SHARP trial were treated with 5 fractions of 6.7 Gy daily for a total dose of 33.50 Gy. the hypofractionated course will allow us to deliver the equivalent of 78 Gy with acute effects equivalent to 46.6 Gy. This appears to be a low total dose for acute reactions, except that it is given in only 5 days.