Stereotactic body radiotherapy shows long-term safety in prostate cancer

By David Douglas

NEW YORK (Reuters Health) - 14/2/2019

Stereotactic body radiotherapy (SBRT) appears to provide good long-term results and very few toxic effects in certain prostate cancers, according to data from thousands of patients.

"This study presents long-term outcomes data indicating that a very short course of radiation, using a higher dose per day, has a highly favorable efficacy and side effect profile for low- and intermediate-risk prostate cancer," Dr. Amar U. Kishan of the University of California, Los Angeles, told Reuters Health by email.

SBRT has been accepted as an effective alternative to conventionally fractionated regimens, but there have been concerns about long-term toxic effects, Dr. Kishan and colleagues note in JAMA Network Open, online February 8.

The researchers examined data from 2,142 men who underwent SBRT between 2000 and 2012. Doses of SBRT ranged from 33.5 to 40.0 Gy in four to five fractions. Treatments were delivered on consecutive days, every other day, or once a week.

Overall, 55.3% of the patients had low-risk disease, 32.3% had favorable intermediate-risk disease, and 12.4% had unfavorable intermediate-risk disease. Median follow-up was 6.9 years.

At seven years the cumulative rates of biochemical recurrence were 4.5% for low-risk disease and 10.2% for all intermediate-risk disease (8.6% for favorable intermediate-risk disease and 14.9% for unfavorable intermediate-risk disease).

Severe toxic events were rare, with a seven-year cumulative incidence of late grade 3 or higher genitourinary events of 2.4% and of gastrointestinal toxic events of 0.4%.

"Our findings suggest that the major trepidation with SBRT - a risk of severe late toxic events - is not supported even with mature follow-up data," the researchers write.

Dr. Kishan concluded, "This approach significantly minimizes the burden of treatment and provides a very convenient alternative to other forms of treatment for this very common disease."

Dr. Rahul Tendulkar, a radiation oncologist at the Cleveland Clinic, in Ohio, told Reuters Health by email that the series "is the largest pooled study of SBRT for early stage prostate cancer in the medical literature to date. It adds robust validity to the observations that prostate SBRT is well tolerated with very few toxic events, has excellent tumor control, and is more convenient for patients that many other treatment options."

"While we await ongoing randomized trials directly comparing prostate SBRT to conventionally fractionated or hypofractionated radiotherapy regimens, the current data suggest that carefully performed prostate SBRT is an effective treatment option that can and should be discussed with most patients with early stage prostate cancer," said Dr. Tendulkar, who was not involved in the research.

SOURCE: https://bit.ly/2E7UV4b JAMA Netw Open 2019

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