A Brief Review of Low-Dose Rate (LDR) and High-Dose Rate (HDR) Brachytherapy Boost for High-Risk Prostate

Abstract

For patients with unfavorable or high-risk prostate cancer, dose escalated radiation therapy leads to improved progression free survival but attempts to deliver increased dose by external beam radiation therapy (EBRT) alone can be limited by late toxicities to nearby genitourinary and gastrointestinal organs at risk. Brachytherapy is a method to deliver dose escalation in conjunction with EBRT with a potentially improved late toxicity profile and improved prostate cancer related outcomes. At least three randomized controlled trials have demonstrated improved biochemical control with the addition of either low-dose rate (LDR) or high-dose rate (HDR) brachytherapy to EBRT, although only ASCENDE-RT compared brachytherapy to dose-escalated EBRT but did report an over 50% improvement in biochemical failure with a LDR boost. Multiple single institution and comparative research series also support the use of a brachytherapy boost in the DE-EBRT era and demonstrate excellent prostate cancer specific outcomes. Despite improved oncologic outcomes with a brachytherapy boost in the high-risk setting, the utilization of both LDR, and HDR brachytherapy use is declining. The acute genitourinary toxicities when brachytherapy boost is combined with EBRT, particularly a LDR boost, are of concern in comparison to EBRT alone. HDR brachytherapy boost has many physical properties inherent to its rapid delivery of a large dose which may reduce acute toxicities and also appeal to the radiobiology of prostate cancer. We herein review the evidence for use of either LDR or HDR brachytherapy boost for high-risk prostate cancer and summarize comparisons between the two treatment modalities.

High-dose-rate brachytherapy with external beam radiotherapy versus low-dose-rate brachytherapy with or without external beam radiotherapy for clinically localized prostate cancer

“…HDR-BT treated more advanced cases than LDR-BT in our cohort. Several retrospective studies 14 – 16 and a few preliminary and premature prospective studies have reported benefits of HDR-BT 17 – 19 .…”

A national surveillance study of the current status of reirradiation using brachytherapy in Japan

“…Advances in external RT with IMRT and image-guided radiation therapy have significantly reduced toxicities and improved outcomes. As a result, use of BT alone or as a boost has diminished over the last decades (21)(22). However, IMRT or stereotactic RT, although highly conformal, is not significantly better than BT in their ability to spare the surrounding previously irradiated tissues (4,19).…”

“…As a result, there is limited opportunity for the general oncologic society to have enough education about ReRT-BT. The American Brachytherapy Society has started a ''300 in 10'' initiative to increase the training of brachytherapists by assisting in the training of 30 oncologists per year over a 10-year period (21), which reflected the status of the present brachytherapy society. Enough experience could lead to more utilization of BT ReRT, as it is likely the responders who have high-level experience with BT would be more likely to perform BT.…”

Does the sequence of high-dose rate brachytherapy boost and IMRT for prostate cancer impact early toxicity outcomes? Results from a single institution analysis

“…Low-dose rate (LDR) and high-dose rate (HDR) BT have both been utilized in prostate cancer [11] . HDR-BT affords several practical, physical, and potential radiobiological advantages over LDR-BT [11] , [12] , [13] .…”

“…Low-dose rate (LDR) and high-dose rate (HDR) BT have both been utilized in prostate cancer [11] . HDR-BT affords several practical, physical, and potential radiobiological advantages over LDR-BT [11] , [12] , [13] . While prospective trials have helped establish the benefit of HDR-BT boost and optimal dose/fractionation regimens [4] , [14] , [15] , [16] , there is no data to rationally inform optimal sequencing of the HDR-BT boost with regards to EBRT.…”