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ItemThe oncological outcomes of dose escalated radiotherapy and its impact on biochemical control and toxicity in men with prostate cancersChao, Michael Wan Tien ( 2019)Introduction: Radiation therapy (RT) for prostate cancer (PC) has steadily evolved over many years, with improvement in biochemical relapse free survival (bRFS). An association between overall survival and doses greater than or equal to 75.6 Gray in men with intermediate and high-risk PC has been reported in population-based studies. Contemporary RT techniques such as image guided radiotherapy, intensity modulated radiotherapy, and stereotactic body radiotherapy, has facilitate further dose escalation. Brachytherapy is an internal form of RT that also developed substantially and can be delivered in combination with external beam radiation therapy (EBRT). However, dose escalation can come with increased gastrointestinal (GI) toxicity and new devices such as rectum spacers have been developed to spare this critical normal structure. Methods: Our large prospective brachytherapy database, that I created, which included patients treated with low dose rate (LDR) and high dose rate (HDR) brachytherapy was interrogated to determine the long-term oncological outcomes. In addition, I was one of the first radiation oncologists in Australia to use a novel polyethylene glycol hydrogel rectal spacer and its iodinated counterpart. We were able to implement its use as a fiducial marker in the post-prostatectomy setting and its use as a tissue expander in the intact prostate for EBRT with or without high dose rate brachytherapy as well as in the post-prostatectomy setting. Results: I found that the use of LDR and HDR brachytherapy with or without EBRT to be safe and efficacious. The bRFS for LDR brachytherapy alone for low to intermediate risk PC was excellent as was its use in combination with EBRT for men with predominantly unfavorable intermediate risk PC. In addition, the use of HDR brachytherapy in combination with EBRT for men with intermediate and high-risk PC also yielded excellent bRFS comparable to any other series reported in the literature. I successfully introduced the use of hydrogel spacers into our practice with marked reduction in rectal volumes irradiated to high radiation doses which allowed appropriate dose escalation of EBRT with or without HDR brachytherapy. This has translated to a marked reduction in late GI toxicity. In addition, we also successfully used hydrogel spacers in the post-prostatectomy setting both as a spacer to allow for ultra-high dose radiation therapy and as a fiducial marker with hydrogel spacer in its iodinated form. Conclusion: Although the use of brachytherapy has declined in the last few years, our results confirm its outstanding efficacy in PC and as such we will continue to advocate for its use. We will continue to support a brachytherapy unit for the treatment of PC. In addition, my work on hydrogel spacers has resulted in its use as standard practice in all PC patients who require EBRT.