Long-term results of MRI-guided partial prostate brachytherapy for favorable-risk prostate cancer: Implications for focal therapy.

Abstract

114 Background: To report long-term results of MRI-guided partial prostate brachytherapy and propose a definition of biochemical failure following focal therapy Methods: From 1997-2007, 318 men with cT1c, PSA < 15, Gleason ≤ 3 + 4 prostate cancer received MRI-guided brachtherapy in which only the peripheral zone was targeted. To exclude benign PSA increases due to prostatic hyperplasia, PSA failure was defined as nadir + 2 with PSA velocity >0.75 ng/mL/year. Cox multivariable analysis was used to determine factors associated with PSA failure. Results: After a median follow-up of 5.1 years (interquartile range: 2.8 to 7.3, maximum 12.1), 26 men failed. While 36 patients met nadir+2 criteria, all eight biopsy-proven local recurrences were among the 26 men who also had a PSA velocity >0.75 ng/mL/year. On multivariable analysis, having intermediate vs. low-risk disease (adjusted HR: 4.4 [95%CI: 1.3-5.5], p<0.001) was the only factor significantly associated with an increased risk of PSA failure. PSA failure-free survival at 5 and 8 years was 95.6% and 90.0% for low risk, and was 73.0% and 66.4% for intermediate risk, respectively. Conclusions: MRI-guided brachytherapy targeting the peripheral zone produced comparable cancer control rates to whole-gland treatment in men with PSA-detected low-risk disease, but may not be adequate for men with “favorable” intermediate-risk disease. Requiring a PSA velocity>0.75 in addition to nadir+2 may be a more appropriate way to define biochemical failure after therapies that target less than the whole gland.