MP17-15 PREDICTORS OF TRANSITION TO WATCHFUL WAITING FROM ACTIVE SURVEILLANCE AMONG MEN WITH LOW-RISK PROSTATE CANCER (FIVO COHORT)

International:Active Surveillance (PRIAS) study.METHODS: PRIAS-JAPAN started in January 2010.37 institutions are participating in this study, and the Institutional Review Boards of the participating centers have approved the study protocol.The inclusion criteria for the PRIAS study are as follows: clinical stage T1c/T2, PSA ¼ 10 ng/ml, PSA density (PSAD) < 0.2 ng/ml per milliliter, one or two positive biopsy cores, and Gleason score (GS) ¼ 6 at initial diagnostic biopsy.Pathological reclassification is defined as the deviation of pathological findings on re-biopsy from the inclusion criteria.Patients are recommended active treatment if the PSA doubling time (PSADT) is <3 years (until December 2014) or if reclassification is comfirmed on re-biopsy.Since 2015, PSADT has become a trigger for extra yearly re-biopsy, and patients are not recommended active treatment because of short PSADT (<3 years).In this analysis, we defined re-biopsy at 1-year as 1st re-biopsy and at 4-year biopsy including extra biopsy as 2nd re-biopsy.We compared the clinical outcome and pathological result of re-biopsy between the group of less than 60 years old (young group) and the groups of over 60 years old or more (aged group).RESULTS: Until September 2017, 768 patients were enrolled and 96 were in young group at enrollment.Patients back ground of young group was as follows: Median age was 56, median PSA was 4.9ng/ml.One positive core was in 73 and two positive cores were in 23.T1c were in 92 and T2a were in 4. At enrollment, the prostate volume of young group was significantly smaller than that of older group.However, there is a not significant difference between both group in PSA value and pathological factors.Re-biopsy rate of young group is lower than that of aged group at 1 year(young group vs aged group; 59% vs 77%)and 4 year(39% vs 47%).Although Re-classification rate of 1st rebiopsy is lower in young group(16.3%vs27.7%), that of 2nd re-biopsy was the equivalent of the value in both group(20% vs 22.5%).After one year and five years, both group shows similar AS remaining rate (one year; 84.2vs 85.7%, five years; 42.2 vs 51.7%).24 patients of young group selected definitive therapy and surgery was the most frequently chosen treatment option.CONCLUSIONS: There is a not significant difference between both group in AS remaining rate.Younger patients tend to avoid re-biopsy but to choose surgery as a definitive therapy.