Method to determine the nadir PSA following partial gland ablation

Area of Science:

• Urology
• Oncology
• Medical Physics

Background:

• Accurate monitoring of prostate cancer treatment is crucial for patient outcomes.
• Nadir prostate-specific antigen (nPSA) is a key indicator following treatment.
• Partial gland ablation (PGA) is an alternative treatment for localized prostate cancer.

Purpose of the Study:

• To propose a novel method for determining nPSA in men undergoing PGA.
• To develop a formula for nPSA calculation specific to PGA treatments.

Main Methods:

• Analysis of two cohorts: 123 men with benign pathology post-transperineal mapping biopsy (TPMB) and 545 men treated with whole-gland brachytherapy.
• Regression analysis to correlate PSA with prostate volume in the TPMB cohort.
• Evaluation of PSA contribution from ablated regions using brachytherapy data and PSA density (PSAD) for untreated volumes.

Main Results:

• A PSAD of 0.12 ng/mL² was identified as significant for men with negative biopsies (R²=0.80, p<0.001).
• In brachytherapy patients receiving ≥220 Gy, 98.2% had PSA <0.2 ng/mL, with a 1.5% positive biopsy rate.
• A formula was derived: nPSA = [(pretreatment PV)-treated volume] × 0.12 ng/mL² for brachytherapy-based PGA.

Conclusions:

• A method to determine nPSA after PGA using brachytherapy was successfully developed.
• The formula assumes complete ablation of the treated volume, excluding its PSA contribution.
• Further clinical validation is recommended for this novel nPSA determination method.