5117 Background: HIFU is an emerging ablative modality for the treatment of localized prostate cancer with limited reports on oncological outcome. We prospectively analyzed our 2-year results. Methods: 253 consecutive patients (age: 64+8) were treated with a planed single session of HIFU using the Ablatherm integrated imaging model system between January 2006 and June 2008. Patients were followed (median: 12; range 3–24 months) with PSA measurement every 3 months. Patients who received prior radiation or hormonal therapy (n=25) and patient for whom at least 2 consecutive PSA measurements were not available (n = 32) were excluded, leaving a total of 196 patients for analysis. Mean pre-treatment PSA was 6.9+3.3. Biopsy Gleason scores at diagnosis (median 9 cores) were 5, 6, 3+4, 4+3 in 1, 91, 66 and 38 patients, respectively. Biochemical failure (BCF) is reported using the Stephenson (PSA >0.4ng/ml and rising), Horwitz (2 consecutive increases of at least 0.5ng/ml) and Phoenix (nadir+2ng/ml) definitions. Results: 196 patients (age: 64+8) met the inclusion criteria for analysis. 75 had low and 121 had intermediate D'Amico's risk stratification disease. Mean and median absolute PSA nadir levels were 0.28+0.53 and 0.06 ng/ml respectively. It was achieved in median time of 3 months and remained unchanged in 70% of the patients throughout the follow-up. Overall 2 years BCF free rates were 70 % (62–78%), 86 % (81–91%) and 96% (91–99%) according to the Stephenson, Horwitz and Phoenix definitions, respectively; with no significant differences between risk groups. Predictors of BCF were absolute nadir [HR: 3.0 (2.3–3.8)] and pre-treatment PSA [HR: 1.1 (1.0–1.2)]. Conclusions: This is the only study to date that analyzed post HIFU BCF free rates according to post radical prostatectomy definition of BCF. BCF usually occur in the first year and plateau thereafter. Short term results by all BCF definitions are promising with similar results for patients with low and intermediate risk. Pre-HIFU PSA and post-HIFU PSA nadir levels are predictors for BCF. [Table: see text]
