Memorial Sloan Kettering has long been recognized as a pioneer in the treatment of cancer with radiation. The collaboration of radiation oncologists and medical physicists has produced the development and clinical implementation of new therapies that are “beyond the standard approaches and definitely not out of the textbook,” in the words of Radiation Oncology Department Chair Simon N. Powell.
Evolving technologies and novel enhancements, many of which were developed by Memorial Sloan Kettering medical physicists, have spurred a number of new clinical initiatives led by radiation oncologists investigating more-effective approaches. One such initiative is a new method for treating pancreatic cancer that eases the burden on patients.
A Challenging Disease
Although pancreatic cancer is relatively uncommon, it is the fourth leading cause of cancer death in the United States. It usually occurs in people older than 55 but is sometimes found in younger people as well. The disease usually does not cause symptoms in its early stages, and when symptoms are felt, they are often mistaken for signs of other illnesses. Because of these factors, pancreatic cancer is often diagnosed only after it has metastasized (spread) to surrounding tissue or other parts of the body.
Radiation therapy plays a vital role in the treatment of pancreatic cancer. If the disease has invaded important abdominal blood vessels and other adjacent structures, surgical removal is impossible. The standard treatment for this type of tumor — when it has not spread to distant organs — is five and a half weeks of daily radiation, with chemotherapy given before, during, and afterward.
But this regimen can be arduous, particularly for older patients, and it has another drawback: During the radiation period, the strength of the chemotherapy must be reduced to avoid toxicity from the combined treatments. This leaves the patient with a less-aggressive system-wide therapy for more than five weeks.
Higher Doses in Fewer Sessions
Memorial Sloan Kettering radiation oncologist Karyn A. Goodman has been investigating stereotactic body radiotherapy (SBRT), a highly precise form of radiation therapy that could shorten treatment time and potentially be more effective. SBRT uses advanced imaging technologies and sophisticated computer guidance to deliver very high doses of radiation directly to tumors. It usually can be given in five or fewer daily sessions.
A clinical trial, conducted jointly by Memorial Sloan Kettering, Stanford University School of Medicine, and Johns Hopkins University School of Medicine, tested the safety of SBRT in about 60 patients with inoperable pancreatic cancer that had not spread. The patients were given the chemotherapy drug gemcitabine (Gemzar®), received five SBRT treatments, and then resumed chemotherapy.
The study was recently completed, and results have been very promising. “We found that patients tolerate this treatment well, with minimal side effects,” Dr. Goodman says. “One concern was that the bigger dose of radiation would cause intestinal bleeding because that occurred in prior SBRT studies done elsewhere. But our patients did not experience bleeding, and giving SBRT with gemcitabine stopped cancer growth and resulted in favorable survival rates for patients as compared with conventional treatment.”
New imaging techniques help ensure the patient is in the same position for every session and that the target area does not shift during treatment. Dr. Goodman has collaborated extensively with medical physicist Ellen Yorke to manage patient motion. To minimize the effects of breathing, patients now wear an inflatable abdominal compression belt.
In addition, Drs. Goodman and Yorke worked to incorporate an x-ray imaging technology on the linear accelerator called IMR, which closely monitors the targeted region during radiation sessions. Tiny gold markers are implanted in the patient as landmarks, and IMR tracks any movement of the gold markers as radiation is delivered.
“We have a little circle on a screen showing where the marker is supposed to be, and if it starts to move outside that circle, we know we need to stop and get repositioned,” Dr. Goodman says.
Dr. Goodman continues to use SBRT on appropriate patients, and hopes to test SBRT head-to-head against the standard treatment in a future trial.
This blog entry is part of a larger feature about advances in radiation oncology published in the October 2013 issue of Center News.