Adding low doses of angiostatin -- a naturally produced substance that inhibits the formation of new blood vessels -- to standard radiation therapy dramatically improves the response to cancer treatment in animal models without increasing toxicity, report researchers from the University of Chicago Medical Center, Harvard Medical School and Northwestern University in the July 16 issue of Nature.
Human angiostatin alone produced only a modest decrease in tumor growth when given to mice with large tumors. Radiation therapy alone produced a slightly greater response. The combination of angiostatin and radiation, however, caused significant growth inhibition, demonstrating a powerful synergistic effect, even in mice with very large tumors.
"Our finding suggests that radiation therapy, already a standard of cancer care, could be dramatically improved by simultaneous administration of relatively small doses of angiostatin," said Ralph Weichselbaum, M.D., professor and chairman of radiation oncology at the University of Chicago and director of the study. "This combination could make radiation much more effective at providing local control of cancer, a crucial part of treatment for many tumors, including prostate, brain, head and neck and other cancers. It could even expand the use of radiation therapy to some forms of metastatic disease without requiring high doses."
The researchers also studied the combination of radiation plus mouse angiostatin against human cancers of the brain, head and neck, and prostate that had been transplanted into mice. Once again, the combination was far more effective than the combined effects of each therapy used alone.
For example, in mice with large radiation-resistant human tumors (SQ20-B, a form of head and neck cancer), angiostatin alone reduced the tumor volume 16 percent, radiation alone reduced volume 18 percent, but combined therapy reduced the average tumor volume 64 percent.