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SBRT vs Conventionally Fractionated, or Moderately Hypofractionated External-Beam Radiotherapy, for Localized Prostate Cancer


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Nicholas J. van As, MBBCH, MRCP, FRCR, MD(res)

Nicholas J. van As, MBBCH, MRCP, FRCR, MD(res)

TREATMENT WITH stereotactic body radiation therapy (SBRT) results in a similar safety profile to conventionally fractionated, or moderately hypofractionated external-beam radiotherapy, in men with low- or intermediate- risk prostate cancer, according to preliminary results of the Prostate Advances in Comparative Evidence (PACE) study, presented by lead investigator Nicholas J. van As, MBBCH, MRCP, FRCR, MD(res).

“These early trial results are promising and help us better understand the effect of different radiation therapy techniques on the treatment of prostate cancer.” Dr. van As is Medical Director and Consultant Clinical Oncologist in the Department of Radiotherapy at the Royal Marsden NHS Foundation Trust in London. He presented preliminary results from the PACE-B arm of this study at the 2019 Genitourinary Cancers Symposium in San Francisco.1

Study Details

THE PACE STUDY is an international phase III randomized controlled trial comparing SBRT to conventionally fractionated, or moderately hypofractionated external-beam radiotherapy, for localized prostate cancer. A total of 874 patients were enrolled by 38 institutions, of whom 845 patients were analyzed. Patients were randomly assigned to receive SBRT (n = 431) and conventionally fractionated, or moderately hyperfractionated radiotherapy (n = 414). Men who were unsuitable for surgery or preferred treatment with external-beam radiation therapy were eligible to participate. The trial evaluated the treatment regimens across multiple effectiveness and safety metrics.

The PACE-B arm of the trial aims to demonstrate noninferiority of SBRT vs conventionally fractionated, or moderately hypofractionated radiotherapy for biochemical or clinical failure. He reported that SBRT was delivered in 5 sessions, whereas conventional radiation therapy was delivered in 20 or 39 sessions. Results from the phase III trial showed that despite the high dose delivered to the prostate, the use of SBRT and conventional radiation therapy resulted in comparable rates of acute gastrointestinal and genitourinary toxicities.

“There has been considerable discussion and analysis of the risks vs the benefits of different radiation treatment techniques, especially in patients with low- or intermediate-risk prostate cancer, in large part because the side effects of treatment can impact quality of life. One of the clinical trial goals was to determine whether SBRT or a more conventionally fractionated radiotherapy schedule would provide a safer treatment choice,” Dr. van As said.

Final outcomes of the trial are expected in 2 to 3 years, and until then, no inference about late toxicity can be made. In the meantime, Dr. van As said, “It’s very encouraging that large doses today are given safely and without significant side effects in the way of acute toxicity and, in fact, better than we expected from the study throughout. We look forward to analyzing additional trial data as it becomes available.”

Follow-up of the study participants is ongoing, and additional data will be analyzed once it becomes available, including results on late toxicities.

DISCLOSURE: Dr. van As has received honoraria and research funding from Accuray, has served in a consulting or advisory role for Accuray and Sanofi, and has received reimbursement for travel, accommodations, and expenses from MSD Oncology.

REFERENCE

1. van As N, Brand D, Tree A, et al: PACE: Analysis of acute toxicity in PACE-B, an international phase III randomized controlled trial comparing stereotactic body radiotherapy to conventionally fractionated or moderately hypofractionated external beam radiotherapy for localized prostate cancer. 2019 Genitourinary Cancers Symposium. Abstract 1. Presented February 14, 2019.


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