The NCI Cancer Bulletin is a font of information (all free, by the way) for a wide array of cancer-related questions. A new post yesterday, “Delving Into Possible Mechanisms for Chemobrain,” suggests that tamoxifen, a drug used to treat breast cancer, can also disrupt cognitive functions. (Tamoxifen, which was approved by the FDA in the 1980s, is used for breast tumors that are estrogen-receptor positive. The NCI has more information on tamoxifen here.)
But what is actually happening inside the brain to cause chemobrain? In other words, what is the mechanism?
Two doctors who study chemobrain intensively — one on the East Coast, one on the West Coast — are looking at that very question. Dr. Timothy Ahles at Memorial Sloan-Kettering Cancer Center in New York is crunching data and looking at the role of genetic changes. He has an additional theory, according to the NCI Bulletin: that patients with chemobrain have cells that cannot repair DNA damage caused by chemotherapy drugs.
Dr. Ahles has been focusing on genes for awhile. When he was at Dartmouth Medical School in New Hampshire, before going to Sloan-Kettering, he and colleagues conducted a preliminary study of 80 cancer survivors. They found that patients with a certain form of the gene APOE were at risk for long-term cognitive decline induced by chemotherapy. The 80 survivors, who had been treated for breast cancer or lymphoma, were given a battery of standard neuropsychological tests. Their blood was drawn and tested for the presence of the APOE gene. The study found differences in test results between those who tested positive for the gene and those who tested negative — particularly in visual memory and spatial ability. “The results of this study provide preliminary support for the hypothesis that APOE is a genetic marker for increased vulnerability to chemotherapy-induced cognitive decline,” Ahles writes in the study.
On the West Coast, Dr. Patricia Ganz, at the UCLA Jonsson Comprehensive Cancer Center, points to inflammation in the brain. Inflammation can be caused by surgery, radiation, chemotherapy or immunotherapy, and it may linger after treatment ends. Dr. Ganz is beginning a pilot study to look at strategies and tactics tht breast cancer survivors can use to combat chemobrain.