Long Term PSA Stability and Predictive Factors of Failure after Permanent Seed Prostate Brachytherapy

Defining biochemical failure as nadir+2 may overestimate cure after radiotherapy. We assess long term PSA stability after low dose rate prostate brachytherapy and predictors of biochemical failure when the PSA is slowly rising below the nadir + 2 ng/ml threshold.

From 1998-2010, 2339 low/ intermediate risk prostate cancers had Iodine-125 brachytherapy with a minimum 3 year follow. 49.7% had 6 months' androgen deprivation. Clinical, dosimetric and PSA data were retrieved from a prospective database. . Biochemical results were classified as stable PSA, rising PSA (≥ 0.2ng/mL and increased ≥ 0.1ng/mL over preceding 2 years) or biochemical failure (defined as nadir+2). Multivariate analysis identified predictors of failure used to create logistic regression models.

At a median follow-up 89 months(37-199), 86% (n=2004) had stable PSA (nadir 0.03; PSA 60-months: 0.04 ng/ml), 6% (n=145) had rising PSA (nadir 0.16; PSA-60: 0.29) and 8% (n=190) had biochemical failure(nadir 0.51; p<0.001). If no prior ADT, PSA nadir (OR: 20.6 p<0.0001) and PSA-60 (OR: 18.3 p<0.0001) were the strongest predictors of failure. The logistic regression model (sensitivity:85%, specificity:98%) predicted failure in 9.8% (8/82). A second model created for the ADT-rising-PSA group using predictive factors PSA-60 (OR: 53.9 p<0.0001) and T-stage (OR: 0.25 p=0.0008), predicted biochemical failure 54% (30/56) [sensitivity:85%, specificity:93%]. The two predictive models yield an anticipated cure rate for the entire cohort of 90%.

Brachytherapy is highly curative with 86% of patients having a stable PSA at a surgical ablation level. Rising PSA is rare (6%) and often innocuous.

The Journal of urology. 2017 Aug 18 [Epub ahead of print]

Audrey Tetreault-Laflamme, Juanita Crook, Jeremy Hamm, Tom Pickles, Mira Keyes, Michael McKenzie, Howard Pai, Francois Bachand, James Morris

CIUSSS de l'Estrie - Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada. Electronic address: ., BC Cancer Agency, Kelowna, BC, Canada. Electronic address: ., Cancer Surveillance and Outcomes, BC Cancer Agency, Vancouver, BC, Canada. Electronic address: ., BC Cancer Agency, Vancouver, BC, Canada. Electronic address: ., BC Cancer Agency, Vancouver, BC, Canada. Electronic address: ., BC Cancer Agency, Vancouver, BC, Canada. Electronic address: ., BC Cancer Agency, Victoria, BC, Canada. Electronic address: ., BC Cancer Agency, Kelowna, BC, Canada. Electronic address: ., BC Cancer Agency, Vancouver, BC, Canada. Electronic address: .

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