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Top Line: Trials using a brachytherapy (BT) boost for high-risk prostate cancer generally give an initial course of external beam radiation (EBRT) to the whole pelvis as opposed to the prostate only.
The Study: Is the pelvic radiation really necessary? This prospective cohort study looks at outcomes from UK centers that began utilizing an EBRT+BT treatment protocol for intermediate- and high-risk prostate cancer. Centers were asked to declare whether they would standardly give pelvic or prostate-only radiation before 15 Gy x 1 high-dose rate brachytherapy. The pelvic regimen was 2 Gy x 23 = 46 Gy and the prostate regimen was 2.5 Gy x 15 = 37.5 Gy. While there ended up being around 400 patients in each treatment arm, the clinical characteristics weren’t so even Steven. In other words, this wasn’t a randomized trial. As one might expect, patients with higher risk features were more likely to receive pelvic radiation, just as they were more likely to receive a longer duration of androgen deprivation therapy (ADT). Nevertheless, multivariable analysis demonstrated that pelvic radiation (even with worse disease characteristics and the interaction with ADT) was associated with a significant improvement in biochemical progression-free survival. When looking at intermediate- versus high-risk patients, it was only the latter who seemed to derive the benefit from pelvic radiation. As expected, though, this came at the expense of higher GI and GU toxicity with larger fields.
TBL: If RTOG 9413 left you confused on the issue, this real-world observational trial supports the efficacy of including the pelvic nodes in radiation treatment volumes for high-risk prostate cancer. | Tharmalingam, Int J Radiat Oncol Biol Phys 2019