1057 THE IMPACT OF PROSTATE CANCER NATURAL HISTORY ON FOCAL ABLATION RESULTS

Article Outline

• INTRODUCTION AND OBJECTIVES
• METHODS
• RESULTS
• CONCLUSIONS
• Copyright

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INTRODUCTION AND OBJECTIVES 

The aim of this study was to analyze the prostate cancer natural history on the results of focal ablation studies, applying the most common definitions of focal therapy success in a group of patients under active surveillance (AS) protocol.

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METHODS 

From March 1993 to April 2009 we identified 258 patients that met the inclusion criteria (PSA ≤10 ng/ml, Gleason score ≤6, ≤ 3 positive cores, no more than 50% of a core involved by tumor) on two staging biopsies and elected to undergo AS. To be included in our AS protocol patients had a second confirmatory biopsy and an endorectal MRI excluding gross tumor. Patients without a third biopsy during follow-up were excluded, leaving a final study population of 160 patients. Three definitions for biochemical recurrence (BCR) commonly used in focal therapy studies were analyzed, including ASTRO definition (three consecutive rises in the PSA), Phoenix definition (nadir + 2ng/ml) and Stuttgart definition (nadir + 1.2ng/ml). Patients with a positive biopsy were considered failure even if the criteria were met. Kaplan-Meier methods were used to plot the probability of success over time for each definition of failure.

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RESULTS 

The median age of the cohort was 64 years, with a median PSA of 4.3 ng/ml. The majority of patients were clinical stage T1c (88%) and had Gleason score 6 (96%) on the first biopsy. After the initial biopsy, 119 (79%) patients had a decrease in their PSA and reached a median PSA nadir of 3.45 ng/ml. Using ASTRO definition the progression free probability at 2 and 5 years was 84% and 59%, respectively. Using the Phoenix definition, 70% and 44% of the patients in AS would be considered free of BCR at 2 and 5 years, respectively, and 59% and 32% at 2 and 5 years if the Stuttgart definition was used. Sixty five patients (41%) had negative biopsies during the follow-up period and would be therefore considered to succeed focal therapy. The probability of having only negative results on the subsequent biopsies was 65% and 34% at 2 and 5 years, respectively (Figure).

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CONCLUSIONS 

Between 32 to 59% of patients would achieve success by focal therapy standards at 5 years even without treatment. In light of this, results of focal ablation studies should be interpreted carefully as a significant number of patients would succeed without receiving any type of therapy.