Edward Cancer Center Treats Lung Cancer With Novel Adaptive Image-Guided Radiotherapy
Clinicians at Edward Hospital here are using Trilogy technology from Varian Medical Systems to offer some cancer patients a novel treatment that adapts to changes in the tumor so that more healthy tissue can be preserved.
This is particularly promising in the treatment of lung cancer, when breathing is already compromised and the doctor must spare as much healthy lung tissue as possible.
In one case, doctors discovered a very large, fast growing tumor in a 69-year-old former smoker who had developed a persistent cough and wheezing. Tests revealed that she had small cell lung cancer, an aggressive form of the disease.
"We needed to use radiation right away to shrink the tumor quickly, because it was collapsing her lung and making it difficult for her to breathe," said Vasudha Lingareddy, MD, medical director of the Edward Cancer Center Department of Radiation Oncology.
Varian's Trilogy technology, equipped with an On-Board Imager device for generating 3-D CT images on the spot, made it possible to pinpoint the tumor each day, fine-tune patient positioning prior to treatment, and see whether the tumor had shrunk enough to reduce the beam size and protect more of the healthy lung tissue. Lingareddy used these images to assess her patient's progress over time and to create new treatment plans that changed as the tumor grew smaller.
"The size of this tumor made it impossible to create a single treatment plan that could avoid harming too much of the surrounding healthy lung tissue," Lingareddy said. "So, our strategy was to replan as the tumor responded to treatment. After a couple of weeks, 3-D images revealed that the tumor had shrunk sufficiently for us to reduce the area being treated by about half. Our patient was elated."
Two weeks later, the clinical team created another treatment plan to better protect the patient's spinal cord, which was approaching the maximum dose that it can tolerate without injury.
"At that point, we generated new 3-D images and used them to create a new plan using beams that completely avoided the spinal cord," Lingareddy said. "This is a big change from how we used to do things, when we'd work out a treatment plan once at the beginning of treatment and then stick with it all the way through a course of treatment. Now, the treatment changes right along with any changes in patient anatomy that we can observe, thanks to image-guidance technology."
The World Health Organization reports that there were over 1.2 million new cases of lung cancer worldwide in 2000, and that the global incidence of lung cancer is increasing at 0.5% per year. A quarter of all cancer deaths in North America are from lung cancer, and 80-90% of these are the result of cigarette smoking.
In addition to lung cancer, Lingareddy and her team are using image-guided radiotherapy protocols to treat cancer of the prostate, breast, liver, pancreas, and head and neck.
According to Lingareddy, the steps involved in adapting a radiotherapy plan based on images were greatly facilitated by the tight integration of the elements that make up the Trilogy treatment system she uses at Edward Cancer Center. "There are other pieces of equipment that would allow you to do daily imaging, but this system makes it easy to use those images efficiently. Simulation is tightly integrated with treatment planning, imaging, and treatment delivery. Once we acquire the 3-D image, we can quickly and easily visualize the tumor response and use that information to modify the treatment plan. It's very efficient for the patient as well as for us, and very accurate."