MRI predicts cancer treatment efficacy
Posted on: 04/19/2005
MRI predicts cancer treatment efficacy
By Philip Svabik, Daily Staff Reporter
April 19, 2005
People diagnosed with brain cancer may soon have access to more effective therapy options, thanks to an advanced MRI scan that can chart the success of a particular treatment early on in the course of therapy, a new University study suggests.
Currently, once a patient is diagnosed with brain cancer, they enter into therapeutic treatment of either radiation therapy or chemotherapy for about six to seven weeks. Patients then must wait six to twelve weeks after the treatment period has ended to return for a follow up image that will prove if the treatment was effective or not.
“If you didn’t respond to the treatment, then you have gone through almost three months of ineffective intervention,” said Brian Ross, a professor of radiology and biological chemistry at the University and one of the study’s 14 authors.
“And now you are faced with the gloomy task of essentially deciding what you are going to select next in consultation with your physician,” he added.
However, Ross and his colleagues have found that by using a special MRI scan, called an MRI diffusion map, they can evaluate the effectiveness of the treatment at a mere three weeks into it — roughly 10 weeks earlier than if standard MRI imaging procedures were used.
Diffusion MRI works by measuring the flow of the water surrounding the brain through the tumor, which helps measure the density of the tumor. The researchers found that if after three weeks there is no diffusion change compared to before treatment was initiated, then the current treatment method is unsuccessful. A more or less dense tumor after three weeks indicates effective treatment. The magnitude of the change in density correlates to the treatment effectiveness, Ross said.
Following the imaging from the MRI diffusion map, Ross said that physicians can then continue the current treatment if it appears to be successful, or he or she can immediately begin a new form of treatment if not.
This time saved is critical to the treatment of brain cancer, which often has a very aggressive nature, Ross said. Not knowing if the treatment is working can cause much anxiety in a patient, he added.
“It is a huge psychological issue by going through treatment for no reason. Is it working? You have no idea,” Ross said.
Diffusion MRI has been used in other applications, such as looking at the brain tissue of stroke victims, but this University study is one of the first to focus on brain tumors and to utilize it for patients.
Ross said that any hospital that already has an MRI could be set up to perform a diffusion map by just adding software.
“Because it’s a physical measurement, it is a quantitative measurement. That is another key aspect because you get a hard number out and that number is translatable and will be the same on any machine throughout the world,” Ross said.
Another contributor to the study, radiation oncology Prof. Theodore Lawrence, believes that diffusion mapping can do more than simply predict early on if a given form of treatment will be effective.
“This test doesn’t just tell who is or is not responding to the treatment, but it also shows the part of the tumor that is responding and it shows the parts that are not responding,” Lawrence said.
Lawrence said that knowing which parts of the tumor are affected and not affected by the treatment could allow doctors to specifically target different parts of the tumor in different ways. One way this could be done would be by the use of Intensity Modulated Radiation Therapy, a type of radiotherapy that can be focused on precise areas.
Presently, the researchers are working to develop a model that will help estimate the cost effectiveness of using MRI diffusion mapping in conjunction with treatment for brain cancer. They also aim to conduct additional trials of this study and to eventually apply their findings to other types of tumors, such as breast and throat cancer.
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