Introduction to HDR brachytherapy

HDR brachytherapy has been used as the brachytherapy component in combination with EBRT for the treatment of prostate cancer [84-90]. In general, for this approach patients undergo transperineal placement of afterloading catheters in the prostate under ultrasonographic guidance. After CT-based treatment planning, several high-dose fractions are administered during an interval of 24 to 36 hours using 192Ir. This treatment is followed by supplemental EBRT directed to the prostate and periprostatic tissues to a dose of 40 to 50.4 Gy using conventional fractionation. Recently, dose-escalation studies have been implemented to increase gradually the dose per fraction delivered with the HDR boost [91]. Improved outcomes with higher HDR boost doses were observed compared with outcomes achieved using lower dose level. Single higher dose fraction also becomes used for dealing with the issue of needle displacement between each fraction [92]. More recently, several institutes have used HDR brachytherapy as monotherapy without the addition of EBRT, largely for low-risk, but also for intermediate- and high-risk patients [93-99].

HDR brachytherapy offers several potential advantages over other techniques. Taking advantage of an afterloading approach, the radiation oncologist and physicist can more easily optimize the delivery of radiation therapy to the prostate and compensate for potential regions of underdosage that may be present with permanent interstitial implantation. Further, this technique reduces involved in the procedure compared with permanent interstitial implantation. Finally, HDR brachytherapy boosts may be radiobiologically more efficacious in terms of tumor cell kill for patients with increased tumor bulk or adverse prognostic features compared with low-dose-rate boost such as 125I or 103Pd.

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