New technology has enabled doctors to administer higher doses of radiation to prostate cancer tumors with fewer side effects; however, escalating the dose of radiation may not help patients with localized prostate cancer in the long term.1
“In the field of radiation oncology, we often assume that the highest dose that the body can tolerate will be most effective at killing cancer,” said Robert Den, MD, a researcher at the Sidney Kimmel Cancer Center at Thomas Jefferson University in Philadelphia, Pennsylvania, and senior author of the study. “Our results argue that this may not be the case, at least not with lower-risk prostate cancer patients.”
The research team conducted a meta-analysis of 12 randomized controlled trials of external-beam radiation treatment for men with nonmetastatic prostate cancer that included a total of 6884 patients.
The researchers chose to examine long-term outcomes, such as the development of metastatic cancer and death from cancer, rather than the prostate-specific antigen (PSA) test that is a typical proxy for patient improvement.
Although PSA levels decreased as patients received higher doses of radiation, improvements did not occur in overall survival and the incidence of metastases.
“It’s important to check our assumptions,” said Adam Dicker, MD, PhD, chair of radiation oncology at the Sidney Kimmel Medical College of Thomas Jefferson University, and coauthor of the study. “This study suggests that our reliance on the PSA test as a proxy for patient outcomes may be not 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.”
They also demonstrated that increasing dose was not associated with worse treatment toxicity, suggesting that current practices are safe.
“These data suggest that other therapies may be needed with radiation to increase survival,” said Den.
1. Zaorsky NG, Keith SW, Shaikh T, et al. Impact of radiation therapy dose escalation on prostate cancer outcomes and toxicities [published online ahead of print March 24, 2016]. Am J Clin Oncol. doi:10.1097/COC.0000000000000285.