Cancer that spreads to the brain is particularly difficult to treat. But researchers say they are gaining a better understanding of how to target these types of tumors. One theory is that a particular type of cell in the brain protects tumors from chemotherapy. The study was reported Sunday at the annual meeting of the American Assn. of Cancer Research in Denver.
About 100,000 cases of brain metastasis (cancer that has spread to the brain) are reported each year in the United States -- far more than the 17,000 cases per year of cancer that originates in the brain. Cancers of the lung, breast, melanoma, kidney and colon are the most likely types to spread to the brain, and metastatic cancer causes the majority of cancer deaths. Scientists at M.D. Anderson Cancer Center in Houston say, however, that a type of cell called an astrocyte that usually ushers oxygen and nutrients to neurons actually protects brain tumors from chemotherapy. The study suggests that cancer metastasis is not random but occurs because certain host tissues offer the right conditions for the cancer to spread and survive.
"To treat brain metastasis we must pay attention to the organ microenvironment, otherwise there is no way chemotherapy can work," said the author of the study, Isaiah J. Fidler, a professor of cancer biology. Fidler and his colleagues are investigating ways to inhibit astrocytes in tumors without interfering with their ability to protect neurons.
Another study presented at the meeting showed that brain tumors that are removed piecemeal are more likely to spread to spinal fluid compared with tumors that are removed intact.
Several factors must be considered when deciding whether a patient should undergo surgery for brain metastasis, said Dr. Raymond Sawaya, chairman of neurosurgery at M.D. Anderson. One of the most critical factors is whether there is metastasis elsewhere in the body. Surgeons can safely remove up to three metastatic brain tumors. Brain mapping and improved surgical techniques have helped improve the survival statistics in patients who undergo brain metastasis surgery, he said.
-- Shari Roan
Photo: An astrocyte. Credit: Ben Ullian / Stanford University