Directing high-energy rays at cancer cells—and away from healthy ones—is a daunting challenge. Now consider that radiation therapy is sometimes being directed at a moving target.
Surgery to remove breast cancer, called a lumpectomy, is typically followed by a series of radiation treatments to help ensure that no cancer cells remain. Doctors use CT scans to help define the tumor cavity and its boundaries, but postsurgical bleeding and swelling may obscure the view. And small variations may translate to dramatic consequences.
A recent study shows that 90 percent of recurrent cases occur within about 1 inch of the tumor cavity. Another study reports that relying on the surgical scar to locate the radiation target often misses the mark.
“When delivering a radiation dose to the tumor bed it is imperative that the treatment plan is accurate,” Dr. Janna Z. Andrews, Indiana University School of Medicine Assistant Professor of Radiation Oncology, Department of Radiation Oncology, explained to the Post. “Traditional CT scans generally offer the ability to visualize the tumor bed seroma (cavity). Then, a generous margin is added to ensure that the tumor bed is in the boost field.”
Experts hope that an advanced ultrasound system from Resonant Medical may help target the treatment area with greater precision and minimize side effects from radiation therapy. The innovative equipment uses noninvasive sound waves to produce 3-D images.
Breast cancer patient Karen Mathis learned about the Clarity system while discussing treatment options with her physician, Dr. Joseph Imperato, who is director of radiation oncology at Lake Forest Hospital in Chicago where the specialized ultrasound unit was installed last year.
“I had heard that radiation can potentially damage other organs,” said Mathis, who recently completed her recommended radiation treatments. “Breast tumors can be close to the heart and lungs. It was very reassuring to me to find out that Dr. Imperato uses the Clarity system to help target the cancer more precisely.”
Dr. Imperato stresses that the evolving ultrasound technology is also cost-effective.
“This is more than a ‘gee-whiz gizmo.’ The addition of ultrasound as an adjunct to CT scanning provides a higher quality of care for the patient, and there is insurance reimbursement,” he says. “A major benefit is the ability to feel very confident that you have localized the true lumpectomy cavity.”
IU cancer specialist Dr. Andrews agrees that the Clarity system offers a unique alternative to target the tumor cavity.
“Using an ultrasound system for verification is an exciting advance because it offers the potential for better accuracy without increasing radiation exposure,” she says. “With better accuracy, margins around the tumor bed may potentially be decreased, and more normal tissue can be spared from the toxicity of a higher radiation dose.”
Additional follow-up data will reveal the long-term impact of using ultrasound to plan and deliver radiation treatments for cancer.
The Clarity system, first approved in 2004 for prostate cancer, is also being tested at select medical centers for treatment of gynecological and bladder cancers. For more information, visit resonantmedical.com.