Intraprostatic calcification and biochemical recurrence in men treated with Cs-131 prostate brachytherapy.

Abstract

237 Background: Vigneault et al. reported that baseline intraprostatic calcification (IC) was associated with a higher risk of biochemical recurrence (BCR) in men treated with I-125 prostate brachytherapy (PB). Cs-131 has different physical properties than I-125. We assessed whether baseline IC was associated with BCR in men treated with Cs-131 PB. Methods: We retrospectively reviewed the records of all low-risk (LR), favorable intermediate-risk (FIR), and unfavorable IR (UIR) prostate cancer patients treated with Cs-131 PB +/- external beam radiotherapy (EBRT) from 2/2011 to 7/2018 at our institution. Patients who received hormone therapy or those with < 24 months follow-up were excluded. Baseline IC status (defined as 1 or more ICs ≥ 5 mm) and characteristics were determined on post-PB CT scans. Baseline patient characteristics were compared via χ2, Mann–Whitney U, or Student’s t-test. Predictors of BCR (Phoenix definition) were analyzed via Cox proportional hazards model and Kaplan–Meier survival curves were generated. Results: Two hundred and sixteen LR, FIR, and UIR prostate cancer patients treated with Cs-131 PB +/- EBRT were included. Median follow up was 56.9 months (range 24.1–111.4 months). 76 patients (35.2%) had baseline IC and 140 patients (64.8%) did not. Baseline disease characteristics did not differ significantly between patients with vs. without ICs. In patients with baseline IC, the median number of ICs was 1 (range 1–3), median length of largest IC was 9.1 mm (range 5.0–33.1), and median peak density of largest IC was 884 Hounsfield units (range 283–1744). ICs were most commonly present in the midgland (88.2%) and central (97.4%) regions. On univariate Cox analysis of all baseline disease, treatment, and IC characteristics, only initial PSA (p = 0.016) and NCCN risk group (p = 0.047) were significant predictors of BCR, whereas baseline IC was not (p = 0.11). The 5-year BCR-free survival in patients with vs. without baseline IC was 97.7% vs. 93.8% (p = 0.40), respectively. Conclusions: In a cohort of LR and IR prostate cancer patients treated with Cs-131 PB, the rate of BCR in men with baseline IC was low and baseline IC was not associated with a higher risk of BCR.