Comparative study of dosimetry between high-dose-rate and permanent prostate implant brachytherapies in patients with prostate adenocarcinoma

Abstract 

Purpose

To compare the dose coverage, conformity, and homogeneity between high-dose-rate (HDR) brachytherapy and permanent prostate implant (PPI) in the treatment of prostate adenocarcinoma.

Methods and materials

From January 2003 to August 2004, 54 patients (108 implants) underwent HDR brachytherapy of prostate cancer with iridium-192 stepping source. Of patients who underwent PPI brachytherapy with iodine-125, 72 patients were randomly selected for the purpose of dosimetric comparison. PPI preplan was done based on transrectal ultrasound study, and postplan was done using CT 1 month after implant. Dosimetric parameters of HDR were compared to that of PPI preplan and postplan.

Results

HDR brachytherapy had lower D₉₀ (111.5% vs. 120.2%), lower V₁₀₀ (97.2% vs. 99.6%), lower natural dose ratio (1.03 vs. 1.13), higher conformal index (0.69 vs. 0.62), and higher homogeneity index (0.63 vs. 0.52) than PPI preplan (all p<0.0001). All the dosimetric parameters of PPI postplan including D₉₀ (86.7%), V₁₀₀ (82.0%), natural dose ratio (0.92), conformal index (0.53), and homogeneity index (0.42) were inferior to HDR brachytherapy (all p<0.0001).

Conclusions

HDR brachytherapy of the prostate can provide better dose coverage, conformity, and homogeneity compared to PPI.

Keywords: High-dose-rate brachytherapy, Permanent prostate implant, Prostate adenocarcinoma, Dose conformity, Dose homogeneity