New Radiation Technology Zeroes In
on Hard-to-Hit Cancers
Recently, Froedtert & Medical College of Wisconsin became one of a handful of healthcare facilities nationwide investigating a new radiation technology with the potential to successfully treat cancers that could not be treated with radiation before. The technology is called TomoTherapy®, and physicians at Froedtert & Medical College of Wisconsin believe it will have a big impact on cancer care. “Tumors don’t usually grow in predictable patterns — such as circles and squares,” says Beth Erickson, MD, a Medical College of Wisconsin radiation oncologist. “They grow in many different patterns that can be difficult to treat with radiation.” It is not just irregularly-shaped malignancies that present a problem for radiation therapy, she adds. The list includes tumors that lie close to critical organs, tumors in parts of the body affected by breathing motion and cancers that develop as multiple lesions.
Two characteristics set TomoTherapy apart from all other radiation therapy systems — its unique dose pattern and built-in imaging unit. Together, they allow TomoTherapy to deliver therapeutic radiation with unprecedented precision. That translates into a greaterability to keep harmful radiation away from healthy tissues, which in turn lets doctors go after cancer with higher radiation doses.
“The TomoTherapy machine looks just like a CT scanner,” says Paul Jursinic, PhD, the director of Clinical Medical Physics at Froedtert & Medical College of Wisconsin. During treatment, a patient lies on a table that moves through a ring-shaped tunnel. At the same time, a linear accelerator (the radiation source) moves in an arc through the ring. The result is a spiral dose pattern.
This unique pattern increases the number of angles at which radiation enters the body. While other systems produce radiation fields from up to nine different points, TomoTherapy can deliver radiation from hundreds of angles. That means less radiation along any particular angle. It also means improved ability to avoid critical organs.
TomoTherapy gains additional versatility from its built-in CT scanner. According to Dr. Jursinic, the scanner allows radiation therapists to check the position of a tumor immediately before and after treatment. “The CT is not diagnostic quality,” he says, “but it is more than adequate for patient positioning and tumor positioning.” The system can also measure the energy that passes through the treatment zone. This allows doctors to calculate the radiation dose being delivered to the patient.
Working in “Real Time”“Imaging has always been key to radiation therapy,” says Dr. Jursinic. “If you can’t see it, you can’t hit it.” That is why he believes TomoTherapy’s onboard CT will have a huge impact on cancer care. “This is true image-guided radiation therapy.”
Typically, days or even weeks can pass between a patient’s initial diagnostic CT and his or her actual therapy. Because tumors can change and grow quickly, treatment plans can become outdated before treatment even begins. Patients undergo a confirming CT before actual therapy, but this presents another challenge — target accuracy. The confirming CT and the radiation treatment take place on different machines, so making sure the patient islined up in the exact same way for imaging and treatment is challenging.
With TomoTherapy, onboard imaging solves both problems. Initial CT scans take place ahead of time as usual. Then, on the day of treatment, TomoTherapy’s low-dose CT provides an instant update on the size, shape and position of the tumor. A built-inplanning computer (another TomoTherapy advantage) lets doctors use the new scan to make on-the-spot adjustments to the treatment plan. Because the CT scan and therapy take place on the same table at the same time, targeting is highly accurate. In addition, physicians can confirm the delivered dose during treatment, which allows for further precision.
TomoTherapy also gives doctors the flexibility to react quickly when tumors shrink in response to treatment. With other systems, confirmation imaging takes place just once a week. According to Dr. Jursinic, TomoTherapy’s instant imaging lets doctors modify the treatment plan every day of therapy if needed.
"With TomoTherapy, we no longer have to plan treatments based on a single, static snapshot of the tumor taken before therapy begins," says Christopher Schultz, MD, Medical College of Wisconsin radiation oncologist. "For the first time, we will have nearly 'real time' information on which to base treatment decisions."
Odd Shapes and Moving TargetsThe Froedtert & Medical College of Wisconsin Cancer Center installed TomoTherapy in July, 2004, tested the system over the summer and began using it to treat patients in September. The Cancer Center is one of only about 20 TomoTherapy “centers of excellence” nationwide. The company that created the new system chose Froedtert for this key role because of its physician expertise, extensive patient base and up-to-date facilities. As a TomoTherapy pioneer, the Cancer Center will help develop the system’s clinical uses. “We are very much in front of the curve,” says Dr. Jursinic.
J. Frank Wilson, MD, Medical College of Wisconsin radiation oncologist and chairman of Radiation Oncology, says early TomoTherapy investigations will focus on hard-to-hit cancers. “We think it could expand the inventory of cancers we can effectively treat with radiation therapy.”
Dr. Erickson, a member of the Cancer Center’s TomoTherapy team, says she and her colleagues in Radiation Oncology will concentrate on malignancies of the chest and upper abdomen, where breathing motion makes cancer a “moving target.” Examples include lung cancer, liver tumors, cancer of the pancreas and bile ducts, and breast cancer. Dr. Erickson says TomoTherapy’s imaging capabilities support treatment techniques that ensure radiation is “on” only when the tumor is in target position.
Dr. Jursinic hopes TomoTherapy will prove effective against irregularly shaped tumors and cancers that lie close to critical structures. Spine tumors are a good example — they can be very long and very close to the spinal cord. “These are difficult to treat conventionally, and right now we don't do it as well as we would like," says Dr. Jursinic. “TomoTherapy, on the other hand, is perfect for it.”
Dr. Jursinic adds that TomoTherapy is well suited for dealing with large or oddly-shaped brain tumors. In addition, since TomoTherapy is able to treat multiple spots with only one patient set-up, it could become a treatment option for cancers that have spread throughout the brain.
Future Is HereLooking ahead, physicians at the Froedtert & Medical College of Wisconsin Cancer Center believe TomoTherapy will let them take advantage of recent advances in functional imaging. Since this type of imaging can yield information on the inner biology of tumors, it could help doctors target cancer more effectively. TomoTherapy, with its superior precision and ability to react instantly to tumor changes, would be the ideal tool.
Dr. Wilson sees functional imaging as a critical tool for future developments in radiation therapy. In fact, combined with Tomotherapy, functional imaging could enable cancer specialists to use tumor biology to guide next generation cancer treatment.
Dr. Schultz, who is part of the team actively investigating new treatment protocols that use TomoTherapy, is excited about the chance to help shape the future of cancer care. “TomoTherapy is taking us where everyone else is probably going in the next decade,” he says, “but it is here now.”
TomoTherapy clinical trials will take place at the Froedtert & Medical College of Wisconsin Cancer Center thanks to funding from the Thomas A. & Lorraine M. Rosenberg Endowment for Clinical Cancer Research.
Source: Froedtert Today
Date: November 2004
Last Review Date: April 26, 2005
Online Editor(s): Tamara Kroll