Prostate Specific Antigen Criteria to Diagnose Failure of Cancer Control following Focal Therapy of Nonmetastatic Prostate Cancer Using High Intensity Focused Ultrasound.

Abstract

We determined whether prostate specific antigen criteria after focal high intensity focused ultrasound to treat prostate cancer could diagnose treatment failure. A total of 598 patients in a prospectively maintained national database underwent focal high intensity focused ultrasound with a Sonablate® 500 device from March 2007 to November 2016. Followup consisted of 3-month clinic visits and prostate specific antigen testing in year 1 with prostate specific antigen measurement every 6 to 12 months and multiparametric magnetic resonance imaging with biopsy for magnetic resonance imaging suspicious for recurrence. Treatment failure was considered any secondary treatment, tumor recurrence with Gleason 3 + 4 or greater disease on prostate biopsy without further treatment or metastasis and/or prostate cancer related mortality. To diagnose failure we evaluated a series of nadir + x thresholds with x values of 0.1 to 2.0 ng/ml. Median patient age was 65 years (IQR 60-71) and the median Gleason score was 7 (range 6-9). Gleason 3 + 4 or greater disease was present in 80% of cases. Tumors were radiologically staged as T1c-T2c in 522 of the 596 patients (88%) and as T3a/b in 74 (12.4%). Baseline median prostate specific antigen was 7.80 ng/ml (IQR 5.96-10.45) in failed cases and 6.77 ng/ml (IQR 2.65-9.71) in cases without failure. Optimal performance according to the Youden index to indicate the most appropriate nadir + x at all analyzed time points at 3-month intervals showed that nadir + 1.0 ng/ml would have 27.3% to 100% sensitivity and 39.4% to 85.6% specificity depending on the time of evaluation in the first 3 years. Nadir + 1.5 ng/ml showed 18.2% to 100% sensitivity and 60.6% to 91.8% specificity with nadir + 2.0 ng/ml leading to similar sensitivity and specificity ranges. Nadir + 1.0 ng/ml at 12 months and nadir + 1.5 ng/ml at 24 and 36 months had 100% sensitivity and 96.1% to 100% negative predictive value. Following focal high intensity focused ultrasound a prostate specific antigen nadir of 1.0 ng/ml at 12 months and 1.5 ng/ml at 24 to 36 months might be used to triage men requiring magnetic resonance imaging and biopsy. These data need prospective validation.