A dosimetric analysis of unstranded seeds versus customized stranded seeds in transperineal interstitial permanent prostate seed brachytherapy

Purpose This study aimed to retrospectively analyze the dosimetric and toxicity results from 272 patients with localized prostate cancer treated consecutively using loose or stranded radioactive seeds by transrectal ultrasound-guided transperineal permanent prostate seed brachytherapy. Methods and materials Two hundred seventy-two patients with localized prostate cancer treated between February 2002 and June 2004 were analyzed. All patients were treated with radioactive iodine-125 or palladium-103 using unstranded or loose seeds (USS) (159 patients) or customized stranded seeds (CSS) at variable spacing (5–50 mm) (113 patients) (Vari-Strand™; BrachySciences, Oxford, CT). A single experienced brachytherapist performed all implants. Results There was a slight improvement in the dosimetric parameter D90 between the CSS (101.9%) and USS (99.3%) groups (p = 0.041). However, overall implant quality based on Radiation Therapy Oncology Group (RTOG) guidelines was similar between both groups. Conclusions We conclude that the D90 value calculated for CSS is statistically improved when compared to the USS cohort, but without a clinically significant difference. There was no difference in the toxicity scores in either group. Overall quality between groups is comparable in our institution.