Low-dose-rate brachytherapy (LDR brachytherapy) with Iodine-125-seeds is an established treatment modality for low- and favourable intermediate-risk prostate cancer. Our single institution experience in this field was retrospectively studied.

Two-hundred sixty consecutive patient records were reviewed for demographic, disease, therapy and side effect data. The patients were divided into subgroups by pre- and post-implant prostate-specific antigen (PSA) levels and by different LDR brachytherapy techniques used, that is, preoperative planning technique (PPT) versus intraoperative real-time planning (IOR). Data were analysed by Kaplan–Meier method and appropriate testing was conducted for PSA biochemical recurrence (BCR) and for toxicities.

After median follow-up of 65·0 months, 94·0% of all patients were free from BCR. This endpoint showed no significant differences by patient age, initial PSA, PSA decrease over time, Gleason score and implanted total activity. Patients with IOR were free of BCR in 98·9% (180/182) versus 76·9% (40/52) with PPT. All patients with a PSA nadir of <0·1 ng/mL were free from BCR. Six patients (2·5%) reported an incontinence grade 1. Transient nocturia/urge and dysuria appeared in 54·7% and 22·6% of patients.

Consistent with literature, LDR brachytherapy for low- and intermediate-risk prostate cancer appeared highly effective for freedom from BCR with mild side effects.

Prostate implants at the British Columbia Cancer Agency are performed using a pre-planned technique. Physicians can augment the dose distribution using one to five non-planned ‘extra’ seeds and this option is determined without intraoperative feedback. The purpose of this research is to quantify the dosimetric impact of extra seeds and to assess the circumstances under which they are considered necessary.

Implanting physicians used a questionnaire to record the three-dimensional location and their rationale for using extra seeds. A plan reconstruction algorithm was used to distinguish the extra seeds from the planned seeds. Distributions with and without extra seeds were calculated to quantify the dosimetric impact to the prostate, urethra and rectum.

Extra seeds resulted in mean relative increases to V100, V150 and V200 of 3·7%, 13% and 19·1%, respectively. Mean prostate D90 increased from 147 to 156 Gy. Improvements in post-implant quality assurance codes were recorded in 30% of the implants with minimal dose increase to the rectum and urethra. Extra seeds were mainly deposited in the prostate anterior–superior quadrant.

The use of two to five extra seeds can result in improvements to pre-planned prostate implants, whereas the costs in terms of increased rectal and prostatic urethral dose are relatively minor.