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ASTRO 2015: A Shorter Radiation Therapy Schedule Can Be as Effective as a Conventional Schedule for Men With Low-Risk Prostate Cancer

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Key Points

  • At a median follow-up of 5.9 years, hypofractionated radiation therapy resulted in similar disease-free survival, compared with conventional radiation therapy for men with low-risk prostate cancer.
  • Estimated 7-year disease-free survival rates were 76% for patients assigned to conventional radiation therapy and 82% for patients assigned to hypofractionated radiation therapy.
  • Both groups reported a similar rate of grade 3 late side effects. Among patients who received conventional radiation therapy, 3% had gastrointestinal side effects and 5% had genitourinary side effects, compared to 5% and 6%, respectively, in the hypofractionated radiotherapy group.

Hypofractionated radiation therapy results in similar rates of cure and side effects compared to a longer treatment schedule for some men with low-risk prostate cancer, according to research (Abstract LBA6) presented by Lee et al October 19, 2015, at the American Society for Radiation Oncology (ASTRO) 57th Annual Meeting in San Antonio, Texas.

Study Details

RTOG 0415 was a phase III study conducted from April 2006 to December 2009 across the United States and Canada that compared the 5-year disease-free survival rate of 1,115 men with low-risk prostate cancer. Patients in the trial were randomly assigned to receive either hypofractionated radiation therapy or a conventional radiation therapy schedule. Baseline characteristics were similar between the two groups, including age (median age = 65) and pretreatment prostate-specific antigen (PSA) scores (median PSA = 5.4 ng/mL).

The primary purpose of the study was to determine whether hypofractionated radiation therapy results in 5-year disease-free survival that is not lower than conventional radiation therapy by more than 7%. The study also looked at overall survival rates and biochemical recurrence.

A total of 1,105 men qualified for the study protocol and were randomly assigned to two groups. Conventional radiation therapy, consisting of 73.8 Gy in 41 fractions delivered over 8.2 weeks was administered to 547 men, whereas 554 men received hypofractionated radiation therapy, consisting of 70 Gy in 28 fractions delivered over 5.6 weeks.

Study Findings

At a median follow-up of 5.9 years, hypofractionated radiation therapy resulted in similar disease-free survival, compared to conventional radiation therapy for men with low-risk prostate cancer. Estimated 7-year disease-free survival rates were 76% for patients assigned to conventional radiation therapy and 82% for patients assigned to hypofractionated radiation therapy.

Comparison of biochemical recurrence and overall survival also met protocol noninferiority criteria. Both groups reported a similar rate of grade 3 late side effects. Of the patients who received conventional radiation therapy, 3% had gastrointestinal side effects and 5% had genitourinary side effects, compared to 5% and 6%, respectively, in the hypofractionated radiation therapy group.

“The results of our study demonstrate that for men with low-risk prostate cancer, hypofractionated radiation therapy offers a shorter, more convenient treatment schedule without compromising cure or causing additional side effects,” said W. Robert Lee, MD, MS, MEd, Professor in the Department of Radiation Oncology at Duke University School of Medicine.

“This is the first large-scale, randomized study demonstrating the value of a shorter course of radiation therapy for low-risk prostate cancer patients,” said Howard Sandler, MD, MS, FASTRO, Professor and Chair of the Department of Radiation Oncology, Cedars-Sinai Medical Center. “The results are not surprising, however, given that studies on the effects of hypofractionated radiation therapy in patients with early-stage breast cancer, which is similar to early-stage prostate cancer, have demonstrated similar outcomes.”

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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