Chemotherapy damages brain cells, according to two studies published this week, leading to memory loss and confusion in cancer patients — and possibly permanent damage in young children.
Cancer patients have long complained of “chemobrain” — a nickname for loss of memory and inability to solve problems and in general think clearly often seen after chemotherapy.
While the effects may wane in adults after a few years, one expert pointed out that the effects may be more permanent in children with growing brains.
Dr. Masatoshi Inagaki of the Breast Cancer Survivors’ Brain MRI Database Group in Japan and colleagues tested more than 200 breast cancer patients, some who had chemotherapy along with surgery and some who did not.
They used magnetic resonance imaging, or MRI, to take detailed pictures of the patients’ brains one and three years after treatment.
A year after 51 patients had chemotherapy, the researchers found significant regions of the brain were smaller -- notably those important to cognition. Cognition includes learning, some types of memory and the ability to understand the surrounding world clearly.
But in 73 patients screened three years after chemotherapy, there were no such differences, Inagaki’s team reported in the journal Cancer.
“Results lead to the idea that adjuvant chemotherapy could have a temporary effect on brain structure,” the researchers wrote.
“These findings can provide new insights for future research to improve the quality of life of cancer patients,” they added.
A second study showed that drugs used to treat cancer may damage normal, healthy brain cells more than the cancer cells they are meant to target.
Joerg Dietrich and colleagues at the University of Rochester in New York worked with human brain cells in lab dishes, exposing them to common chemotherapy drugs such as cisplatin, carmustine and cytarabine. They also soaked cells from real human tumors in the drugs.
The drugs killed more brain cells than tumor cells, they report in Thursday’s issue of the Journal of Biology, published by BioMed Central.
Low doses of the chemotherapy drugs killed 60 percent to 90 percent of brain cells called oligodendrocyte precursor cells and neuron precursor cells, but had little effect on most of the cancer cells.
To kill 80 percent of cancer cells, doses that killed 70 percent to 100 percent of the brain cells were required.
When they treated live mice with the drugs, Dietrich’s team found that brain cells in the mice continued to die for at least six weeks after the end of treatment.
Dr. Patricia Duffner, a neurologist at the University of Buffalo School of Medicine in New York, said radiation therapy on the head had long been known to affect intelligence.
“Cranial irradiation can be so devastating to the brains of young children (under three to five years) that, by the mid-1980s, many families opted not to treat babies and very young children who had malignant brain tumors,” she wrote in a commentary in the same journal, published on the Internet at http://jbiol.com/content/5/7/22.
“Very high-dose chemotherapy, requiring bone marrow transplantation or peripheral stem cell support, is now standard therapy for children with certain brain tumors, especially for the very young,” she added.
“There are no easy answers. We must balance the need for survival with quality of life.”