Radiation oncology: MR and CT taking on bigger roles
September 16, 2016
by Lauren Dubinsky
, Senior Reporter
“The goal of radiation therapy for cancer is to [administer] the radiation accurately into the cancer without irradiating too much healthy tissue,” says X. Allen Li, professor and chief of medical physics at the Medical College of Wisconsin. He intends to do that with the new Elekta MR-linac system that’s soon to be installed at the college. The system integrates a radiotherapy system, a high-field MR scanner and software that allows the physicians to see the patient’s anatomy in real time. They’re able to locate the tumor and stay on track during delivery, even when the tumor tissue moves or changes shape, location or size.
Elekta initiated its MR-linac Consortium in 2012 along with Royal Philips. Since then, the University Medical Center Utrecht in the Netherlands, The University of Texas MD Anderson Cancer Center and The Netherlands Cancer Institute have installed the system. The standard of care for radiation therapy relies on CT, but it’s not able to identify soft tissue for many tumor sizes, says Li.
Benefits of MR
The major advantage of MR is its ability to image soft tissue, which allows the tumor to be targeted more accurately. In the past, radiation therapy could treat pancreatic cancer within 1 centimeter of the target lesion, but MR allows for accuracy within 5 millimeters. “The tumor or normal tissue may change due to the radiation delivery,” says Li. “MR can identify that type of behavior so we can adjust the radiation for the patient. That personalizes the radiation therapy delivery.”
Dr. Brian Kavanagh, chair of the department of radiation oncology at the University of Colorado and president-elect of ASTRO, also believes that MR-linac may offer advantages over the current standard. “The MR can often give a sharper image than a CT scan, depending,on the body part you are looking at, and this by itself could be a valuable advantage,” he adds. MR can also provide more information on tumor physiology and response to treatment, even while the treatment is still ongoing. That additional data can be translated into actionable information that could lead to modifications early in treatment based on the patient’s tumor response.
Despite the advantages, it’s going to take a while for hospitals to adopt MR to assist with radiation therapy, says Li. The early adopters are working to rigorously design clinical trials to demonstrate how the technology can help patients. “Once we start to see the clinical impact and the outcome change and the cost of the technology drops, then the pace of adoption will increase,” says Li.
Planning with CT
CT might not be the optimal choice for guiding treatment, but it is useful for treatment planning. A CT simulator helps the oncology team create patient models using the CT data and then calculates the radiation dose that should be administered. Philips Healthcare’s Brilliance CT Big Bore is one of the CT simulators on the market. It’s larger than a diagnostic CT because it needs to accommodate patient setup and it has a rigid tabletop to ensure there’s minimal deflection when the patient is on the table.
X-ray was the original imaging modality used for radiation therapy planning, but over the last four to five years CT has replaced it. CT is now considered the accepted standard of care for simulation treatment planning, says Jennifer Bryniarski, senior product manager of oncology and CT at Philips. MR is also being increasingly used for radiation therapy planning. It has advantages for certain body parts where soft tissue contrast is needed, but CT remains superior because of its iterative reconstruction algorithms.
What’s new this year?
In late June, Accuray received FDA clearance for its next-generation TomoTherapy System, the Radixact Treatment Delivery Platform, which includes the Accuray Precision Treatment Planning System and iDMS Data Management System. This new platform expands access of treatment to a wider range of cancer patients, including those who are being re-treated. Accuray told HealthCare Business News that while other systems offer image-guided intensity-modulated radiation therapy (IMRT), the TomoTherapy System is specifically designed for that purpose.
Using the system’s TomoHelical delivery mode, physicians can target the tumor continuously, administering the dose 360 degrees around the patient. This next-generation platform has a more powerful linear accelerator and offers low-dose fan beam megavoltage CT imaging and helical treatment delivery. It also features automated workflows and mid-course, decision-making tools, so the clinicians can modify treatment delivery based on changes in tumor size, shape and location.
Its ability to provide daily image guidance is what makes it unique. The system takes an image of the patient every day, as part of the setup, so that it knows exactly where the tumor is on that particular day. “As the [cancer patient goes] through the treatment process, anatomical changes may occur, such as the tumor shrinking or the patient losing weight,” says Kelly Londy, chief operating officer at Accuray. “Clinicians need to be able to quickly determine when these types of changes warrant modifying the treatment and efficiently creating new treatment plans.” Competitor systems are designed with a C-arm gantry. The TomoTherapy System is built on a ring gantry platform with a CT scanner.
In late July, a study that shows the benefits of TomoTherapy for low-risk breast cancer patients was published in AntiCancer Research, International Journal of Cancer Research and Treatment. After 34 months, there was no recurrence of cancer in the treated breast and over 95 percent of the patients and their physicians rated cosmesis as good/excellent. Some facilities have purchased the TomoTherapy System to use solely for breast radiotherapy, according to Accuray. The new Radixact System will be commercially launched in the first quarter of fiscal year 2017.
The global radiotherapy market was worth $5.59 billion in 2015 and is expected to reach $7.54 billion by 2020, according to a MarketsandMarkets report. Technological advancements in radiotherapy systems, the growing elderly population, increasing prevalence of cancer globally and symposiums that drive investments in radiotherapy are expanding the market. The leaders in the market are Varian, Elekta and Accuray. Varian estimates that it has over 50 percent of the global radiotherapy market, pertaining to linear accelerator technology, stereotactic radiosurgery and other cancer treatment systems that utilize X-ray.
Radiation therapy in Africa
The challenges of communicable diseases have been addressed to a good enough extent in Africa to allow more people to live longer. But now the continent is dealing with higher incidences of cancers in the elderly population. “Expansion of the field of radiation oncology in Africa, in particular, is driven by the rising importance of cancer as a public health challenge,” says Kavanagh. “In one sense, that is not all bad and actually represents progress.”
Modern radiotherapy technology has been installed in the region over the past few years. In early August, Varian Medical Systems was selected to supply Clinac iX systems to Ethiopia to treat the more than 90 million people in the region. A major hurdle that Africa is experiencing is the lack of people with the skills to maintain and operate the equipment. Varian and others are working to change that.
“What we have been trying to do is bring experience from people who use the equipment all of the time, create a training program and train people within the country,” says Corey Zankowski, vice president of product and solutions portfolio at Varian. “[Then we plan to] set up a large enough entity in the country, so they can sustain and train more and more care providers in the region.”
Dr. Patricia Hardenbergh, a radiation oncologist at Shaw Regional Cancer Center in Edwards, Colorado, has developed a website called chartrounds.com. It’s an educational forum for discussions on difficult cases between clinicians on the front lines and experts from academic medical centers. After gaining popularity in the U.S., Hardenbergh is expanding it to allow for international access to meet the demands for radiation oncology education in developing countries.
Wil Ngwa, a medical physicist at the Dana Farber Cancer Institute, has been leading several international initiatives. He organized a symposium in April, in which representatives from African nations and leading international health agencies discussed ways to collaborate. Varian is working to bring radiation oncology training to India, Brazil, Algeria, Vietnam, Turkey and some parts of Russia. “We have been doing this kind of work around the globe, primarily with governments that are really interested in working on adding radiation oncology to their cancer plan,” says Zankowski.
ASTRO sneak peek
Radiation oncologists from around the world gather at the American Society for Radiation Oncology (ASTRO) annual meeting to learn about the latest research in the field. More than 11,000 people attend the event each year. This year it will be held from Sept. 25-28 in Boston. One of the studies to be presented will address the concerns about disparities between racial groups regarding access to technology such as stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT).
“It would be tragic if safe and highly cost-effective treatments like stereotactic radiotherapy were not available widely to everyone who could benefit from it,” says Kavanagh. The question is whether or not there is a difference in insurance status for minorities and the rest of the population. The Affordable Care Act allowed more people to gain access to insurance, but cultural barriers still need to be addressed. A few of the ways Kavanagh thinks it can be solved is by providing education to groups about the proper ways to screen and treat cancers, support networks to help people get to and from their treatments and patient navigators that help keep track of appointments for tests and treatments.
Another study to be presented at ASTRO will assess the implementation of new technology in the Veterans Affairs setting. This health care delivery system has come under scrutiny for instances where resources may not have been used in an ideal manner, says Kavanagh. “It’s good to see efforts where physicians are paying attention to whether patients appear to be getting state-of-the-art treatments at the right time, delivered safely and effectively,” he adds. “It was comforting to see that there is access to the newest radiation treatment technology and that it’s utilized in a good way.”