One of the challenges of treating cancer is that it is literally a moving target. Between the initial diagnosis and the first day of radiation therapy, a tumor may change in size, shape and even position. If we can target the cancer more precisely, that is, “see” it better, we can treat it more effectively. An innovative technique called image-guided adaptive therapy makes that possible.

Delivering more accurate, personalized cancer treatments

The idea behind image-guided adaptive therapy is to use imaging systems like MRI to accurately identify the borders of a tumor and the surrounding organs as close as possible to the time the patient receives the treatment. Over the last decade, physicians and researchers with the Froedtert & the Medical College of Wisconsin Cancer Network have evolved technologies and expertise to make this shift toward more personalized radiation therapies possible. The latest advance in adaptive technology is Elekta’s high-field MR-guided linear accelerator, or MR-linac.

First-in-the-world cancer technology

Developed by a Swedish company, Elekta, and its Netherlands-based MRI technology partner, Philips, the Elekta MR-linac is the world’s first radiation therapy technology to combine a modern linear accelerator (linac) with a high-field MRI scanner into a single device. Previous radiation therapy systems relied on separate CT imaging and linac treatment devices for treatment planning and treatment delivery. Compared to CT-based imaging, MRI imaging has the advantage of identifying normal and abnormal soft tissue with great clarity. This characteristic alone has the potential to give doctors unprecedented power to visualize and treat soft tissue cancers, such as those in the head and neck, brain, breast, esophagus, lungs, liver, pancreas, cervix, rectum, and prostate gland.

The major breakthrough with the MR-linac is that these clearer MRI images are obtained as part of the treatment process. The better imaging characteristics of the MR-linac and the ability to acquire imaging immediately before, during and after every treatment session allows the treatment to be adjusted to the exact tumor position at that moment - rather than based on images that were acquired days or weeks before treatment.

This shortens the radiation treatment process from days or weeks to minutes. And it enables radiation therapy treatments to tightly conform to a tumor’s shape so doctors can give a tumor a much higher dose of radiation, while simultaneously avoiding surrounding normal tissues. For patients, this can result in fewer treatments, improved tumor control and potentially fewer side effects.

Researchers at the Froedtert & MCW Clinical Cancer Center at Froedtert Hospital are part of Elekta’s MR-linac Consortium — an international research team of academic medical centers studying the advanced capabilities of MR-linac technology. The Froedtert & MCW Clinical Cancer Center is one of just two founding members of the consortium based in the U.S. The other center is The University of Texas MD Anderson Cancer Center in Houston.

Designed to treat all types of cancer

The MR-linac was designed for people with all types of cancers who are treated with radiation therapy today. It can also treat people who have cancers that were previously considered unsuitable for or hard to treat with radiation therapy. For example, because of its ability to adapt, the MR-linac may be particularly effective for people with tumors that are in constant motion. This would include a tumor in the lung that moves with each breath — or pancreatic, liver and other upper abdominal tumors that also move with a person’s breath — and that may wrap around blood vessels or lie close to organs such as the stomach that don’t tolerate radiation therapy well.

U.S. FDA premarket clearance for the MR-linac is anticipated in late 2018. At the Froedtert & MCW Clinical Cancer Center, physicians will begin testing the technology in a clinical trial that focuses on pancreatic cancer patients. The new technology will be available for certain cancer patients in the U.S. soon after FDA clearance.

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About the Author

Christopher Schultz, MD, is the chairman of radiation oncology, researcher and MCW faculty member with the Froedtert & MCW Cancer Network. He also chairs the clinical steering committee for the Elekta MR-linac Consortium and is one of a team of oncologists, physicists and others leading MR-linac research at the Froedtert & MCW Clinical Cancer Center.

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