Parameters predicting for prostate specific antigen response rates at one year post low-dose-rate intraoperative prostate brachytherapy

Abstract

Purpose

To develop a model for prostate specific antigen (PSA) values at one year among patients treated with intraoperatively planned ¹²⁵I prostate brachytherapy (IOPB).

Material and methods

Four hundred and deven patients treated with IOPB for prostate adenocarcinoma were divided into four groups: those with PSA values ≥ 3 ng/ml; < 3 and ≥ 2; < 2 and ≥ 1 or PSA < 1 between 10.5 and 14.5 months post implantation (1yPSA). Ordinal regression analysis was then performed between patient, tumor, and treatment characteristics. 1yPSA values were also compared with toxicity outcomes.

Results

Median 1yPSA was 0.77 (0.04-17.36). Thirty-two patients (8%) had a PSA ≥ 3; 35 (9%) had PSA < 3, ≥ 2; 87 (21%) had PSA < 2, ≥ 1, and most patients 254 (62%) had PSA < 1. PSA response was independent of gland volume, Gleason score, clinical stage, seed activity, V ₉₀, V ₂₀₀, D ₉₀, or number of needles and seeds used. Older patients had significantly lower 1yPSA; median ages 65.1 (46.5-81.0), 62.1 (50.4-79.5), 60.5 (47.1-80.3), and 58.1 (45.1-74.2) years for each of the 1yPSA groups respectively ( p < 0.001). Also, both implant V ₁₅₀ ( p < 0.001) and initial PSA values ( p = 0.04) were predictive of 1yPSA values. There was no correlation between 1yPSA values and toxicity encountered.

Conclusions

PSA response at 1 year post IOPB appears to be dependent on patient age, initial PSA, and implant V ₁₅₀. Our results provide reassurance that parameters other than biochemical failure influence 1yPSA values.