I-125 LDR Prostate Brachytherapy in a United Kingdom Centre: Evolution of a Technique

Abstract

Purpose: LDR prostate brachytherapy has been performed at the Royal Surrey County Hospital, since 1999. During this time numerous modifications have been made to the process. These changes have been made not only with the availability of new technology, but also with innovations brought about by experience. Such modifications have brought about improvements in dosimetry and toxicity. This evolution of technique is described here. Materials andMethods: In 1999, the modified Seattle technique was used. This was a two-stage procedure, which required patients to undergo preplanning 2e4 weeks prior to implant. Patients underwent TRUS in the extended lithotomy position. Transverse sections of the prostate, urethra and rectum were outlined at 5mm intervals, and the digitized TRUS images were used to create a plan. The plan aimed to give a minimum peripheral dose of 145Gy to the prostate. At implantation, loose seeds were placed using pre-loaded needles, and peripheral stranded seeds were used. No intraoperative planning was undertaken during this period, although the placement of needles took into account the intraoperative imaging, in addition to the pre-plan. CTwas initially performed at Day 28, but more latterly at Day 1 or Day 0. From 2005, a novel approach was developed in response to concern regarding potency and catheterisation rates. Loose seeds used centrally, were implanted individually, extending around the margins of the apex, but taking care to avoid the rectum, urethra and penile bulb. Peripheral stranded seeds were used as previously. By 2007, intraoperative planning had become available. This allowed adjustments to the plan, based on dosimetric analysis intraoperatively, by altering the number and position of the loose seeds. From 2006, patients with outflow obstruction due solely to median lobe hypertrophy were offered a bladder neck resection (BNR) approximately 6 weeks before their implant, which meant that this treatment option was available to a subset of patients who had previously been excluded. In 2008, in the light of the availability of intraoperative planning, a one stage technique was developed. Since then, patients have undergone TRUS volume estimation in the clinic, by taking a five set measurements, instead of a formal ‘‘Stage 1’’ TRUS. A nomogram has been developed based on these measurements, to allow seed ordering prior to implantation. From this nomogram, the number and length of peripheral needles and the likely number of loose seeds, are calculated. Once the peripheral seeds have been implanted, a plan is created to determine the number and placement of the central loose seeds. Results: Actuarial data from over 1600 patients reveals a 93% 5 yr bRFS, which is unchanged when compared to the first 300 patients treated in this center. When the novel technique was compared to modified Seattle, there was a improvement in dosimetry (D90 155Gy vs. 147Gy, p 5 0.03, V100 91.7% vs. 90.7%, p 5 0.29) This was also associated with an improvement in potency from 61.7 to 83.3% at 2 years (p 5 0.008). In those patients who underwent BNR for LUTS, implant was achieved without apparent detriment to urinary function (change in IPSS at 6 months for patients undergoing BNR was 3.7 and that for controls was 5.7 (p 5 0.08)). In 1999, the duration of anaesthesia for implant was 30e45mins, whereas in 2010, the same time is taken for a one stage procedure. Conclusions: Experience and developing technology have permitted the development of a brachytherapy technique that is increasingly convenient to the patient and clinician. Improved toxicity has been achieved without detriment to efficacy.