Dr. Robert Nordal, assistant professor at the University of Alabama-Birmingham (UAB) and radiation oncologist at UAB’s Wallace Tumor Institute, notes that radiation oncology is not familiar territory to many doctors outside the cancer field. “It is not one of the standard rotations, like internal medicine or pediatrics, so some people haven’t had any acquaintance with it,” he said.
Many people confuse radiation oncology with radiology. They both make use of imaging technology from X-rays to CT scans and MRIs, but radiology is diagnostic in nature, while radiation oncology is about treating cancer.
“Two-thirds of people diagnosed with cancer will end up receiving radiation,” pointed out Dr. Sandra Tincher, radiation oncologist with Brookwood Cancer Care Center. “Most of the radiation treatments we do are curative, but many physicians believe radiation treatment is all palliative.”
Dr. Susan Salter, radiation oncologist with St. Vincent’s-Birmingham, says if there’s one thing she would like physicians to know about radiation oncology, it’s that this is part of cancer treatment. “Cancer can be treated in multiple modalities, including radiation, surgery and chemotherapy.”
According to the American Society for Therapeutic Radiology and Oncology, patients with one of three cancers — breast cancer, prostate cancer and lung cancer — make up more than half of all patients receiving radiation therapy. For most cancer types treated with radiation therapy, at least 75 percent are treated with the intent to cure the cancer, rather than control the growth or relieve symptoms like pain. (For lung and brain cancers, that number is somewhat lower.)
The most common type of radiation treatment is an external beam treatment from a linear accelerator, but there are other methods of delivering radiation, including brachytherapy (seed implant) treatments and gamma knife (used for brain treatment).
“Radiation’s been used to treat cancer for more than 100 years, since the discovery of X-rays by Roentgen and others in the late 1800s,” Nordal said. “Almost immediately it was realized that tumorous growths were diminished when exposed to radiation.”
Of course, radiation oncology today is much more sophisticated, and tremendous advances have been made in the last decade. These advances fall into two areas, according to Nordal: biologic research, which combines radiation with targeted biological therapies, and therapies that make use of the power of computers and advanced imaging techniques.
For instance, he explained, “Fifteen years ago, the patient was imaged on a type of X-ray platform, and the radiation oncologist almost visually aimed the radiation beam. Now the patient’s anatomy is captured with a scan, a CT or MRI or both, transferred into a computer, and a radiation plan is developed in the computer. This allows 3-D rendering of anatomic structures as well as the tumor.” A “beam’s-eye view” allows the radiation oncologist to view relationships between the tumor and the patient’s anatomy along the axis of the radiotherapy beam.
Some of the newest radiation therapies being offered in the Birmingham area include the following:
- Intensity-modulated radiation therapy, or IMRT. It uses computer-controlled X-ray accelerators to deliver precise radiation doses to a tumor. “This allows us to use computing power to optimize the radiotherapy plan in much greater sophistication than time would ever allow one to do manually,” Nordal said.
- Image-guided radiation therapy, or IGRT. It uses various imaging technologies (such as CT, MRI, PET/CT) to locate a tumor target prior to a radiation therapy treatment. This allows the amount of healthy tissue exposed to radiation to be reduced.
- TomoTherapy. This allows real-time CT-image-guided IGRT and IMRT. This is a slice-based radiation therapy that replaces the use of a traditional two-dimensional X-ray image with a CT image for localizing the desired treatment area. “You are actually visualizing the tumor (and the surrounding anatomy) every day with a CT scanner and delivering the radiation,” Salter explained.
- Bexxar therapy, which is a monoclonal antibody that has a radioactive substance attached to it. The antibody seeks and binds to a protein receptor on the surface of malignant cells. Once bound to the target cells, Bexxar delivers radiation, which enhances the killing effect of the antibody. “It has been very successful in treating recurrent low-grade lymphomas,” Salter said.
- High-dose-rate MammoSite therapy. After a breast cancer tumor is removed via a lumpectomy, a soft balloon is placed inside the lumpectomy cavity through a catheter, inflated with saline solution, and a radiation seed is inserted into the balloon to deliver the radiation therapy.
- Partial breast irradiation therapy, which can be delivered via a MammoSite catheter or via the more traditional linear-accelerator method.
“There have been some tremendous advances in technology for the delivery of radiation,” Tincher said, “that allow us to deliver higher doses of radiation more safely, and limit the toxicity from the treatment.”
November 2007