January 11, 2012
The University of Rochester Medical Center has been a leader in the study of stereotactic body radiation therapy (SBRT) for the past decade, and two of the latest research projects show that SBRT is emerging as an important tool for more people with advanced cancer.
Alan W. Katz, M.D., M.P.H., and Michael T. Milano, M.D., Ph.D., in separate studies in the International Journal of Radiation Oncology, Biology, Physics, report that SBRT can lead to long-term survival for liver cancer patients who are awaiting a transplant, and for select patients with early metastasis of many types of cancer.
Their work is the latest from a body of research conducted at the URMC’s James P. Wilmot Cancer Center, which was among the first institutions in the country to use SBRT. The therapy delivers high doses of radiation precisely to the tumor without harming adjacent tissues. Doctors use a coordinate system to map their target, and then deliver multiple, intersecting radiation beams at the spot, like several flashlights focused in one area. Because of their early use of this technology, Wilmot scientists have been able to study patients for longer periods under a variety of circumstances.
“Although we have known for quite some time that it is possible to treat metastatic disease, the technology needed to catch up to the concept,” said Milano, an associate professor of Radiation Oncology at Wilmot. “Now, physicians have a greater comfort level with SBRT due to treatment and imaging technology that can pinpoint smaller tumors, and data from our institution and others showing that SBRT works very well in certain cases.”
Katz, who is also an associate professor of Radiation Oncology, agreed. “Compared to older, more invasive treatments, stereotactic body radiation is usually very well tolerated, particularly as a bridge treatment,” he said. “And many people who develop liver cancer also have serious underlying conditions such hepatitis and cirrhosis of the liver, so often they are not candidates for chemotherapy and they are looking for novel, less-invasive ways to delay progression of their disease.”
In fact, SBRT is particularly useful for liver cancer. Patients seeking a liver transplant must meet the transplant criteria after a typical year-long waiting period. Bridge therapies are required during this time to keep the disease from spreading, and to improve chances for long-term survival.
Katz’s study was small, involving 18 patients initially and then only 12 who qualified for a transplant a few months after receiving SBRT between 2007 and 2009. However, the survival outcomes were significant: approximately 19 months after surgery all patients were doing well with no recurrences and no significant toxicities from the treatment, Katz said. (Average five-year survival rates for liver cancer vary greatly, ranging from 10 percent to 60 percent, depending upon the stage at diagnosis and other factors.)
Milano studied the long-term outcomes of 121 people who were treated with SBRT after being diagnosed with recurrences from a variety of cancers, including breast, prostate, lung and colon. Only people with five or fewer metastatic lesions were eligible. Breast cancer patients fared the best, perhaps because that cancer tends to be more indolent, he said.
For example, half of the 39 breast cancer patients with metastasis survived for more than four years after SBRT, and one-third of them were alive at seven-year follow-up visits. The study also noted that for the breast cancer patients who had bone metastasis, after SBRT none of their lesions recurred.
With other types of cancer, SBRT was less successful in terms of long-term survival but still was useful at controlling new lesions and thus delaying further spread of the disease in 74 percent of the patients. The two-year overall survival rate for 82 patients with metastasis from colon, lung, esophagus, or sarcomas, was 39 percent. Seven of 82 patients were alive after seven years.
When cancer spreads from the original site in the body to another site, the chances of a cure are slim. The primary goal is to slow the disease and relieve symptoms. Future research is aimed at investigating the newer, targeted treatments that might offer the best chance at prolonging life while maintaining quality of life.
Milano said further study of SBRT should address which subgroups of patients, aside from people with breast cancer, are likely to derive the most benefit from SBRT, and at what doses. When the URMC first began studying SBRT in 2001, 5-Gy fractions of radiation delivered to the organs was considered novel. Since then, however, researchers and clinicians have shown that doses of 10 to 20 Gy can be safe and effective, and the higher doses could potentially result in even better long-term survival.
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