Four of these studies have been large, randomized, multi-center phase 3 clinical trials reported in 2016 and 2017 that demonstrated the non-inferiority of hypofractionated radiation regimens compared with conventional radiotherapy: the Prostate Fractionated Irradiation Trial (PROFIT), the Conventional vs Hypofractionated High-Dose Intensity-Modulated Radiotherapy for Prostate Cancer (CHHiP) trial, RTOG-0415, and the Hypofractionated vs Conventionally Fractionated Radiotherapy for Patients With Localized Prostate Cancer (HYPRO) trial.3-6

Moderate hypofractionation is delivered using intensity-modulated radiotherapy (IMRT). Following the recent clinical trial results, moderately hypofractionated IMRT is now considered a standard of care, Dr Chen said.

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Stereotactic body radiation therapy (SBRT) is used to deliver “ultra-hypofractionation,” which can deliver radiation therapy even more quickly — in just 1 week, Dr Chen added.

“This is a promising technology and many prospective studies have shown that this seems to be safe and effective,” Dr Chen said. “There are several randomized trials ongoing at this time comparing SBRT to longer treatments using IMRT.”

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Following publication of large, randomized clinical trials conducted in the United States, Canada, and Europe, the American Society for Radiation Oncology (ASTRO) created a task force, co-chaired by Dr Morgan, to develop an evidence-based clinical practice guideline about hypofractionated radiation therapy for localized prostate cancer, in collaboration with the American Society of Clinical Oncology (ASCO) and the American Urology Association (AUA).

Definitive ultra-hypofractionation can deliver the total therapeutic radiation dose in just 5 fractions, Dr Morgan noted. Results from single-arm trials of ultra-hypofractionation conducted to date are “very promising,” he added.

Whereas the case for moderate hypofractionation is relatively strong, the evidence base for definitive ultra-hypofractionation for localized prostate cancer is, according to Dr Morgan, “substantially less mature at present. A number of large-scale randomized studies are under way but, to date, none have reported efficacy results. The literature at present consists largely of prospective single-institution and multi-institutional cohort studies.”

Yet now researchers are turning their attention to hypofractionated radiotherapy in the postsurgical setting.