Debate 2: The Case for Focal External Beam Radiation Therapy Boost Over Brachytherapy Boost for Prostate Cancer.

Modern trials demonstrate excellent outcomes for men with localized prostate cancer treated with radiation therapy. However, some patients experience recurrences, and more than one-third of recurrences are localized to the prostate. Treatment intensification through dose intensification could substantially benefit some patients with localized, unfavorable-risk prostate cancer. Currently, modern phase 3 randomized controlled trials support 2 treatment strategies. ASCENDE-RT evaluated whole-gland LDR brachytherapy boost, and FLAME evaluated a focal external beam radiation therapy (EBRT) boost to MRI-visible lesions. This review compares a FLAME-style EBRT boost vs a LDR brachytherapy boost in terms of oncologic outcomes, toxicity, and feasibility. The FLAME trial demonstrates that an EBRT boost to MRI visible lesions improves local control as well as regional and distant metastasis free survival without a significant increase in toxicity. In contrast, ASCENDE-RT reports an improvement in only biochemical recurrence free survival, and this comes at the expense of increased gastrointestinal and genitourinary toxicity. Beyond efficacy and toxicity, we discuss the challenges to widespread implementation of each technique, as treatment advances are only beneficial if they are available. While both techniques have unique barriers to implementation, we believe addressing the barriers for focal EBRT boost implementation are more addressable. In conclusion, we maintain that available high-level evidence supports a focal EBRT boost over brachytherapy because focal EBRT boost was shown to give a meaningful improvement in oncologic outcomes with minimal impact on quality of life.