A higher dose of radiation increases survival for men with medium- and high-risk prostate cancer, but not those with low-risk disease, according to a study by researchers from Penn Medicine, now online ahead of print in JAMA Oncology (doi:10.1001/jamaoncol.2015.2316).
“Our study raises the provocative question of whether radiation dose reduction for patients with low-risk prostate cancer could achieve similar cure rates while avoiding the increased risk of side effects associated with higher radiation doses,” said the study's lead author, Anusha Kalbasi, MD, a radiation oncology resident at Perelman School of Medicine at the University of Pennsylvania.
He and his colleagues used the National Cancer Database and analytic methods to compare the survival rates of 42,481 men in the absence of a randomized clinical trial. For men with medium- and high-risk prostate cancer, every incremental increase in radiation dose resulted in an approximately eight and six percent reduction, respectively, in the rate of death from any cause. For men with low-risk cancer, there were no differences in survival whether or not they received the standard dose or a higher dose.
First to Show the Link
The study, which was funded by the National Cancer Institute, is the first to link increased radiation dose with higher survival rate, the researchers said, noting that previous studies have linked increased radiation dose with steady PSA scores and the absence of tumor regrowth following successful radiation.
The study included men who were diagnosed with prostate cancer between 2004 and 2006 and followed through 2012. In 2004, 56 percent of these men received higher dosages of radiation, whereas now, that figure is approximately 90 percent, the researchers noted.
In the low-risk group of men, the seven-year adjusted survival rates were 86 percent for both those who received the standard dose and those who had the higher dose. In the medium-risk group, those survival rates were 82 and 78 percent, respectively; and in the high-risk group, those survival rates were 74 and 69 percent, respectively.
Kalbasi noted that the side effects of radiation therapy—fatigue, urinary frequency and urgency, changes in bowel habits, and erectile dysfunction—have been shown to increase with radiation dose.
The study's senior author, Justin Bekelman, MD, Associate Professor of Radiation Oncology at Penn, said: “Our findings show that the dose of radiation should be personalized to the specific characteristics of the prostate tumor. For some patients, personalized treatment will lower the chances of toxicity while maintaining similar survival rates; for others, it will mean escalating radiation dose to achieve the highest survival while protecting normal tissues, like the bladder and rectum.”