Original paper Evaluation of the dosimetric impact of loss and displacement of seeds in prostate low-dose-rate brachytherapy

Abstract

PurposeTo analyze the seed loss and displacement and their dosimetric impact in prostate low-dose-rate (LDR) brachytherapy while utilizing the combination of loose and stranded seeds.Material and methodsTwo hundred and seventeen prostate cancer patients have been treated with LDR brachytherapy. Loose seeds were implanted in the prostate center and stranded seeds in the periphery of the gland. Patients were imaged with transrectal ultrasound before implant and with computerized tomography/magnetic resonance imaging (CT/MR) one month after implant. The seed loss and displacement had been analyzed. Their impact on prostate dosimetry had been examined. The seed distribution beyond the prostate inferior boundary had been studied.ResultsThe mean number of seeds per patient that were lost to lung, pelvis/abdomen, urine, or unknown destinations was 0.21, 0.13, 0.03, and 0.29, respectively. Overall, 40.1% of patients had seed loss. Seed migration to lung and pelvis/abdomen occurred in 15.5% and 10.5% of the patients, respectively. Documented seed loss to urine was found in 3% of the patients while 20% of patients had seed loss to unknown destinations. Prostate length difference between pre-plan and post-implant images was within 6 mm in more than 98% of cases. The difference in number of seeds inferior to prostate between pre-plan and post-implant dosimetry was within 7 seeds for 93% of patients. At time of implant, 98% of seeds, inferior to prostate, were within 5 mm and 100% within 15 mm, and in one month post-implant 83% within 9 mm and 96.3% within 15 mm. Prostate post-implant V100, D90, and rectal wall RV100 for patients without seed loss were 94.6%, 113.9%, and 0.98 cm3, respectively, as compared to 95.0%, 114.8%, and 0.95 cm3 for the group with seed loss.ConclusionsSeed loss and displacement have been observed to be frequent. No correlation between seed loss and displacement and post-plan dosimetry has been reported.

Plan reproducibility of intraoperatively custom-built linked seeds compared to loose seeds for prostate brachytherapy

“…Wang et al . [ 32 ] reported that the prostate post-implant V 100 , D 90 , and rectal wall RV 100 for patients without seed loss were 94.6%, 113.9%, and 0.98 cm 3 , respectively, as compared to 95.0%, 114.8%, and 0.95 cm 3 for the group with seed loss; there were no correlations between seed loss due to migration and post-plan dosimetry. Miyazawa et al .…”

Focal partial salvage low-dose-rate brachytherapy for local recurrent prostate cancer after permanent prostate brachytherapy with a review of the literature

“…Wang et al . reported that it had no impact on the implant quality of initial whole prostate LDR brachytherapy [ 22 ]. However, in focal partial re-implantation, it is necessary to avoid seed migration to maintain implant quality.…”

Low dose rate permanent seed brachytherapy: tracing its evolution and current status

“…Furthermore, local movement of seeds with the prostate might affect the sectoral dose, whereas dosimetry of the whole prostate might be unaffected. Clinical results have not yet been able to implicate these local migrations to a reduced possibility for cure 72 . Distant migration of seeds to lungs or other vital organs can cause temporary self‐limiting side‐effects, such as bloody sputum, pneumorrhagia, pneumothorax, and also late sequelae, including secondary cancers 73,74 …”