UF study: Proton therapy shows unprecedented promise in prostate cancer
Published: Monday, February 24, 2014 at 4:44 p.m.
Last Modified: Monday, February 24, 2014 at 4:44 p.m.
The University of Florida Proton Therapy Institute in Jacksonville, one of just 14 such centers in the U.S., recently released results of a study on men with prostate cancer that might be the most promising with the therapy yet.
The vast majority of prostate cancer patients enrolled in the study were living cancer-free five years after the proton beam treatments.
The study looked at 211 patients with low-, medium- and high-risk disease. Ninety-nine percent of low- and medium-risk patients had no evidence of disease after five years, compared with 76 percent of high-risk patients. That's nearly a 10 percent improvement over previous studies.
"We are very positive about our results; we don't know anyone else who has reported better results," said Dr. Nancy Mendenhall, medical director of the Proton Therapy Institute and lead author of the study, which was published in the online edition of International Journal of Radiation Oncology, Biology and Physics.
"We're just beginning to see the tip of the iceberg of the benefits with this technology," Mendenhall continued.
"We're most excited about medium-risk patients."
For those patients, other studies have at best reported a 90 percent five-year survival rate.
The reason, Mendenhall speculates, is that the treatments at UF were delivered faster, and over a shorter time period.
"We think we can go faster because with protons, most radiation is put on the target and very little outside. With IMRT and any kind of X-ray-based therapy, most of the dose is deposited outside of the target — and injuries result in side effects and complications," she said.
IMRT, which stands for intensity-modulated radiation therapy, is what most patients get. But protons are more precise and can be used in higher dosages, especially for delicate areas of the body such as the spine and brain. Because of this precision, proton therapy avoids damaging nerves surrounding the prostate that could lead to erectile dysfunction and incontinence.
Proton beam therapy also has been used successfully to treat pediatric tumors. A previous study at the Proton Beam Therapy Institute from the fall found that more than 90 percent of children treated at the institute since 2006 survived more than two years, with brainstem side effects affecting just 2 percent of the children.
"This study provides important evidence that proton therapy may be safely delivered to our most vulnerable patients with delicate tumors," said Dr. Daniel Indelicato, an associate professor in the department of radiation oncology at UF.
The median age of the children in the study was 5.9, and most had tumors near the brainstem, the path between the brain and spinal cord where most of our neurological functions are centered.
"The role of proton therapy in most pediatric brain and skull base tumors is widely accepted by national and international consensus," Indelicato said. "This is because the pediatric central nervous system is very sensitive to the damaging effects of (traditional) radiation."
Radiation also can damage a child's central endocrine system, which controls hormones responsible for development.
"To the extent that proton therapy may reduce the radiation dose to these systems, it is regarded as an improvement on traditional radiation," Indelicato said.
One of the more controversial aspects of proton therapy is its cost, which is roughly $50,000 per patient.
That's 1.2 to 1.7 times as expensive as IMRT treatment, Mendenhall said.
However, Medicare covers it, as do many insurance companies, she added.
"Most insurance companies have been OK with that because they know that there's going to be less toxicity that they have to pay for later, and maybe fewer recurrences," she said.
In other words, the long-term payoff is perceived to be greater with proton therapy because it might be more effective at nipping cancer in the bud rather than prolonging the need for treatment.
Still, prostate cancer patients ideally would be diagnosed earlier, when they are most likely to have low-risk disease, Mendenhall said. But national guidelines — from the U.S. Preventive Services Task Force — two years ago recommended against PSA screening for prostate cancer screening for men in the general population. High-risk men are still advised to get screened.
An elevated PSA had long been considered a sentinel for prostate cancer, but with fewer men getting screened, overall surveillance in the general population has gone down.
"Without surveillance, they are diagnosed with medium or high-risk disease," Mendenhall said. "We've been seeing a much higher percentage of patients with medium and high risk disease."
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