A Dose of Precision
Stereotactic radiation therapy—heavily marketed to consumers—is gaining momentum as a more convenient treatment. But it’s not for every patient.
By Sharon Reynolds
Depending on where you live, you may have seen advertisements touting a seemingly painless cancer treatment approach, using language such as “Imagine treating cancer with knifeless surgery” or “No surgery. No pain. No recovery time. No tumor.”
The ads, promoting technologies that go by names such as CyberKnife or the Edge, are part of a wave of direct-to-consumer marketing of a type of radiation therapy called stereotactic radiation, which holds promise for delivering focused and precise radiation that targets tumors and minimizes damage to surrounding tissue. While the ads may lead the average person to believe stereotactic radiation therapy puts a cure easily within reach, the technology isn’t for every cancer patient. It is most commonly used to manage cancer that has metastasized—to delay cancer progression rather than cure the disease—or to destroy small tumors in patients too sick to withstand surgery.
“It’s a really exciting technology and it can be great technology in some circumstances,” says Amol Narang, a senior resident in radiation oncology at the Johns Hopkins University School of Medicine in Baltimore. Narang sees stereotactic radiation being adopted at a rapid pace, but notes some expanded uses still need to be tested in clinical trials.
Visualizing a Better Approach
Radiation therapy—the use of high-powered X-rays or charged particles to kill cancer cells by damaging their genetic material—has been a cancer treatment for more than a century. But the advent of computed tomography and magnetic resonance imaging, first adopted in medicine in the 1970s, changed the field of radiation oncology over the decade that followed. These imaging technologies allowed radiation oncologists to better map patients’ tumors so they no longer had to use large radiation fields to make sure they actually hit the targets. Radiation oncologists can now capture images of the tumor and surrounding areas just moments before delivering treatment, reducing the chance that radiation will inadvertently hit healthy tissues if a patient shifts or takes a breath.
“People cured tumors [before modern imaging and computing], but it was at a greater price in terms of side effects because you’d have to treat lots of normal tissue in order to encompass the tumor,” says Theodore S. Lawrence, a radiation oncologist at the University of Michigan in Ann Arbor, who witnessed firsthand a decrease in side effects among his patients resulting from improved imaging technologies and more precise radiation technology. (See “Radiation Side Effects
Technology like stereotactic radiation therapy, which closely sculpts the dose of radiation to the tumor, also allows doctors treating various types of cancer to give higher doses of radiation than ever before, which some studies suggest may enhance the likelihood that a targeted tumor will not come back.
Stereotactic radiation therapy was first used to treat brain metastases in the 1990s. The results of early trials using stereotactic radiation therapy in treating other cancers in the body were first published in the early 2000s. Offering high accuracy and precision, stereotactic radiation therapy can deliver an entire course of radiation therapy in just one to five large, precisely targeted doses—sometimes in just over a week. By comparison, a standard course of radiation therapy can include dozens of small doses given once a day five days a week for weeks and sometimes up to two months.
Successes and Cautions
Evidence from clinical trials supports the use of stereotactic radiation for patients with small tumors—less than 5 centimeters in diameter—that have metastasized, or spread, to other organs, such as the liver or the lungs. In many cases, if these secondary tumors can be controlled, patients can expect to live for several years with a good quality of life.