About 20-40 percent of all patients with cancer will develop brain metastasis (tumours that have spread from elsewhere in the body) at some point during the course of the disease. Survival for patients with untreated brain metastasis is generally less then 7 weeks.
The most common procedures used to treat brain metastasis are invasive, time consuming, or require specialized equipment or physician training. However, a team of Lawson Health Research Institute scientists have found a possible alternative.
What We Know
Cancer that has spread to the brain is difficult to cure; however, current treatments can help control the cancer and reduce symptoms.
“Most commonly, daily radiation treatments given to the whole brain over 1-2 weeks have been used for this purpose,” notes Dr. Glenn Bauman, Lawson scientist and Radiation Oncologist at the London Regional Cancer Program at London Health Sciences Centre (LHSC) and Chair of the Department of Oncology at The University of Western Ontario. This treatment will provide tumour control and symptom relief in about half of patients.
“More recently, surgery or highly focused radiation treatments (known as stereotactic radiosurgery) directed at individual spots of cancer in the brain, combined with whole brain radiation therapy has been found to have the best results,” says Dr. Bauman. “This treatment course can improve tumour and symptom control, particularly if there are only a small number (one to three) of spots of cancer.” However, neither of these treatment options is without drawbacks.
Surgery requires hospitalization for the procedure and is associated with some discomfort and a lengthy recovery time. Furthermore, surgery may be impractical if there is more than one spot, or if the cancer is located in a critical area or deep in the brain.
Stereotactic radiosurgery (SRS), which is a non-surgical procedure that delivers a single high-dose of precisely-targeted radiation on the specific area of the brain where the tumour resides, requires specialized equipment and training that is not routinely available in all cancer centres. In addition, there is still some discomfort, inconvenience and added expense associated with SRS procedures. According to a survey by the Canadian Association of Radiation Oncology, there are only three cancer centres in Ontario that are able to provide SRS. Consequently, it is very likely that this treatment is underutilized in Ontario, potentially shortening the survival time of a large number of patients.
“Knowing this information, we asked ourselves if there was a way we could get similar benefits for our patients without the use of SRS or surgery,” said Dr. Bauman.
What We Did
In a recent study Lawson’s Dr. Bauman and Dr. George Rodrigues, who is also a radiation oncologist at LHSC, used a new technology called “helical tomography” as an alternative to surgery or SRS for the treatment of patients with cancer spread to the brain. The helical tomotherapy unit looks similar to a diagnostic CT scanner. It combines CT diagnostic imaging capability with the ability to deliver therapeutic radiation doses with high precision. In 2004, the London Regional Cancer Program at LHSC was the third centre in the world to receive one of these units which are now in widespread clinical use worldwide.
“Based on a pre-clinical technology assessment, we felt that this treatment machine had the potential to do what was necessary to deliver highly precise and conformal radiation therapy. We have successfully used it to treat other cancers such as prostate, but we had not heard of any published reports of using this technology for the treatment of brain metastases,” says Dr. Rodrigues.
The researchers have just completed a Phase I trial which is used to test the safety of a new treatment course. “We wanted to find out what was the safest most effective dose level we could use,” says Dr. Bauman.
Using this unit, the researchers gave a low dose of radiation to the whole brain but at the same time gave increasing amounts of radiation boosts to the individual metastases.
What they found was that they could safely treat the individual tumours with twice the amount of radiation therapy as the rest of the brain, with no additional side effects and no dose limiting toxicity experienced by the patient. “The side effects profile of this new treatment appears to be consistent to those that we would get using SRS, but the treatment is less invasive and did not require a separate treatment session like SRS,” says Dr. Rodrigues.
By using the helical tomotherapy unit, patients across Ontario would have access to the best treatment for brain metastasis currently available.
Next Steps
Drs. Bauman and Rodrigues have been sharing their results with other clinicians. During the month of October Dr. Bauman presented to the Canadian Association of Radiation Oncology and Dr. Rodrigues was recently in Chicago presenting at the Annual Meeting of the American Society for Radiation Oncology.
They are now planning a Phase II trial to begin in the new year. This trial will examine the technique in a larger number of patients at the target level identified during the Phase I trial.
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