Abstract
BackgroundLow risk prostate cancers are commonly treated with low dose rate (LDR) brachytherapy involving I-125 seeds. The implementation of a ‘live-planning’ technique at the Royal Adelaide Hospital (RAH) in 2007 enabled the completion of the whole procedure (i.e. scanning, planning and implant) in one sitting. ‘Live-planning’ has the advantage of a more reliable delivery of the planned treatment compared to the ‘traditional pre-plan’ technique (where patient is scanned and planned in the weeks prior to implant). During live planning, the actual implanted needle positions are updated real-time on the treatment planning system and the dosimetry is automatically recalculated. The aim of this investigation was to assess the differences and clinical relevance between the planned dosimetry and the updated real-time implant dosimetry.MethodsA number of 162 patients were included in this dosimetric study. A paired t-test was performed on the D90, V100, V150 and V200 target parameters and the differences between the planned and implanted dose distributions were analysed. Similarly, dosimetric differences for the organs at risk (OAR) were also evaluated.ResultsSmall differences between the primary dosimetric parameters for the target were found. Still, the incidence of hotspots was increased with approximately 20% for V200. Statistically significant increases were observed in the doses delivered to the OAR between the planned and implanted data; however, these increases were consistently below 3% thus probably without clinical consequences.ConclusionsThe current study assessed the accuracy of prostate implants with I-125 seeds when compared to initial plans. The results confirmed the precision of the implant technique which RAH has in place. Nevertheless, geographical misses, anatomical restrictions and needle displacements during implant can have repercussions for centres without live-planning option if dosimetric changes are not taken into consideration.
Highlights
Low risk prostate cancers are commonly treated with low dose rate (LDR) brachytherapy involving Iodine 125 (I-125) seeds
Given that the LDR seed implant programme at Royal Adelaide Hospital (RAH) started in 2004 and that the 2 step live planning procedure with manufacture pre-loaded needles did not start until Nov 2007, it was felt that during the studied period all staff involved in prostate brachytherapy were experienced in the procedure
The results obtained using the methodology outlined previously were divided into two sections: one for the treated volumes, i.e. prostate and Planning Target Volume (PTV), and the other for the organs at risk (OAR)
Summary
Low risk prostate cancers are commonly treated with low dose rate (LDR) brachytherapy involving I-125 seeds. The implementation of a ‘live-planning’ technique at the Royal Adelaide Hospital (RAH) in 2007 enabled the completion of the whole procedure (i.e. scanning, planning and implant) in one sitting. A common treatment option for low grade prostate cancers is low dose rate (LDR) seed brachytherapy. It is usually employed as a monotherapy. Developments of this treatment technique would implant the seeds into the prostate via retropubic surgery. This was later improved so that the seeds were implanted via the perineum without the need for surgery [1]. These needles were implanted after aligning the planning US images of the prostate with the live US images of the prostate as seen on the implant day
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