Increased radiation doses for prostate cancer have not increased survival

By John Murphy, MDLinx
Published March 31, 2016

Key Takeaways

New technology has allowed oncologists to increase the doses of radiation administered to patients with prostate cancer, which has resulted in significantly improved outcome measures of “freedom from biochemical failure” (FFBF)—a marker of more serious patient outcomes.

But new research shows that increased radiation for treating prostate cancer has not improved those more serious outcomes—including overall survival, distant metastasis, and cancer-specific mortality, according to a study published online March 24, 2016 in the American Journal of Clinical Oncology.

“We often assume that the highest dose that the body can tolerate will be most effective at killing cancer,” said the study’s senior author Robert Den, MD, Associate Professor of Radiation Oncology, Cancer Biology, and Urology at the Sidney Kimmel Cancer Center at Thomas Jefferson University, in Philadelphia, PA. “Our results argue that this may not be the case, at least not with lower-risk prostate cancer patients.”

For most clinical trials, FFBF is identified as reductions in prostate-specific antigen (PSA) levels. PSA is used for screening, risk stratification, as an indicator of treatment success for individual cancer patients, and as a surrogate for patient outcomes in clinical research.

For this study, Dr. Den and colleagues conducted a meta-analysis of 12 randomized-controlled trials of external beam radiation therapy performed on a total of 6,884 patients with non-metastatic prostate cancer. They found that PSA levels decreased as patients received higher doses of radiation, but overall patient survival, incidence of distant metastasis, and cancer-specific mortality did not improve. 

“These data suggest that other therapies may be needed with radiation to increase survival,” Dr. Den said.

“It's important to check our assumptions,” added study co-author Adam Dicker, MD, PhD, Chair of Radiation Oncology at the Sidney Kimmel Medical College of Thomas Jefferson University. “This study suggests that our reliance on the PSA test as a proxy for patient outcomes may not be as useful as many researchers thought, which has broad implications for the design of future clinical trials and the interpretation of current and previous studies.”

The study also demonstrated that increasing doses of radiation did not correlate with greater toxicities, which indicates that current treatments are safe.

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