Does prior transurethral resection of prostate compromise brachytherapy quality: A dosimetric analysis

Abstract

To evaluate, in a retrospective review, prostate brachytherapy dosimetry outcomes relative to the transurethral resection of the prostate (TURP) cavity size to address the theoretical concern that an intraprostatic cavity may hinder adequate radioactive source placement. A total of 73 patients who underwent prostate brachytherapy as part of their treatment of localized prostate cancer had a history of a prior TURP. Of these 73 patients, 37 underwent (125)I implantation, 19 (103)Pd implantation, and 17 partial (103)Pd implantation. The dose was calculated using the dose to 90% of the prostate gland (D(90)) from the 1-month post-implant dosimetric analysis. The doses were normalized relative to 100% of the prescription dose. Archived transrectal ultrasound images were used to determine the maximal length and width of the visible residual TURP cavities. The prolate spheroid or symmetric egg shape was used to calculate each residual cavity volume. The derived volume of the TURP cavity was divided by the measured ultrasound volume of the prostate at brachytherapy, creating a percentage of volume measurement for each prostate. All p values, unless otherwise specified, were generated by comparing patients without a visible TURP defect with the subgroups of patients with a visible defect using the Student t test. A visible residual TURP defect was noted on the operative transrectal ultrasound images of 55 (75%) of the 73 patients with a history of TURP before brachytherapy. The 18 patients without a visible TURP defect had a median D(90) of 96% and were used for subsequent statistical comparison. Thirty-six patients with a TURP defect <10% of the entire prostate volume had a median D(90) of 109% (p = 0.02). Thirteen patients with a TURP defect between 10% and 20% of the prostate volume had a median D(90) of 112% (p = 0.03). Six patients with a TURP defect >20% of the prostate volume had a D(90) of 89% (p = 0.43). A visible residual TURP cavity that is assumed to have a prolate spheroid shape and occupy >/=10% of a prostate volume did not appear to be a statistically significant hindrance to proper dosimetric outcome.