Class solution in inverse planned HDR prostate brachytherapy for dose escalation of DIL defined by combined MRI/MRSI

Abstract

Purpose-To establish an inverse planning set of parameters (class solution) to boost dominant intra-prostatic lesion (DIL) defined by MRI/MRSI.Methods-For 15 patients, DIL were contoured on CT or MR images and a class solution was developed to boost the DIL under the dosimetric requirements of the RTOG-0321 protocol. To determine the maximum attainable level of boost for each patient, 5 different levels were considered, at least 110%, 120%, 130%, 140% and 150% of the prescribed dose. The maximum attainable level was compared to the plan without boost using cumulative dose volume histogram (DVH).Results-DIL dose escalation was feasible for 11/15 patients under the requirements. The planning target volume (PTV) dose was slightly increased, while the DIL dose was significantly increased without any violation of requirements. With slight adjustments of the dose constraint parameters, the dose escalation was feasible for 13/15 patients under requirements.Conclusion-Using a class solution, a dose escalation of the MRI/MRSI defined DIL up to 150% while complying with RTOG dosimetric requirements is feasible. This HDR brachytherapy approach to dose escalation allows a significant dose increase to the tumor while maintaining an acceptable risk of complications. KeywordsClass solution; Dominant intra-prostatic lesion; MR Spectroscopy imaging; Dose escalation; Inverse planned HDR brachytherapy High dose rate (HDR) brachytherapy can safely and accurately deliver radiation dose to prostate cancer with a single Ir-192 source. The HDR brachytherapy employs catheters inserted directly into the prostate, guided by transrectal ultrasound (TRUS), and adjusts source dwell times along the catheters with a remotely controlled afterloader. Advancements recently made in imaging technology have improved the accuracy and effectiveness of HDR prostate brachytherapy planning. The anatomical information obtained from computed [2,4,17,18,25,26]. In addition, the development of anatomy-based inverse planning dose optimization for HDR brachytherapy can produce a highly conformal dose profile within one minute, with more than 90% of the prostate volume covered with the prescribed dose and a clinically acceptable sparing of OAR [1,3,5,[13][14][15]28]. Furthermore, the concept of class solution commonly used in intensity modulated radiation therapy (IMRT) [8,20,21,24,27] is now available in brachytherapy. The class solution of an inverse planning routine can reduce the variation of treatment plan quality across different users and can dramatically decrease the treatment planning time. In this study we developed a class solution for boosting MRI/MRS defined DILs in inverse planned HDR brachytherapy of prostate cancer. HHS Public Access Methods and materials Patient cohortsWe used data from 15 HDR patients with MRI/MRSI de-fined DILs (patients A to O). The mean ± standard deviation value of their prostate volume was 43.7 ± 16.3 cc with a range from 28.1 to 86.0 cc. In general, 16 catheters (range from 15 to 18) were inserted using TRUS gu...

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Evaluation of the interfractional biological effective dose (BED) variation in MammoSite high dose rate brachytherapy

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