Common cancer drugs may be more harmful to the brain than the tumor cells they are meant to destroy.
Cancer chemotherapy can damage the brain, killing crucial brain cells and causing key parts of the brain to shrink, according to the study conducted by researchers at the University of Rochester Medical Center and published in the Journal of Biology.
Laboratory tests have shown that dose levels typically used when treating patients killed 70-100 per cent of neural cells but just 40-80 per cent of cancer cells. Several types of healthy brain cell continued to die for at least six weeks after exposure. Even though the cancer drugs are targeted at replicating cancer cells, the researchers found that both replicating and non replicating brain cells were killed.
Cancer patients who receive chemotherapy have long complained of adverse neurological side effects ranging from memory loss to, in extreme cases, seizures, vision loss and even dementia. Until very recently, these conditions were often dismissed as unrelated to the cancer treatment and rather the result of the patient’s mental state.
Mark Noble, from the University of Rochester Medical Centre in New York, who led the research, said: “This is the first study that puts ‘chemo brain’ on a sound scientific footing, in terms of neurobiology and cellular biology.”
The brain is populated with several types of cells that produce or repair normally functioning neurons. These are classified as dividing stem cells, dividing intermediate cells, precursors and progenitors, and non-dividing mature cells. Dr Noble’s team exposed healthy brain cells as well as cancer cells to three chemotherapy drugs, carmustine, cisplatin and cytosine arabinoside, used to treat a wide range of diseases, including breast cancer; leukemia and brain tumors. Tests showed that the drugs were toxic to all the different cell types even at very low concentrations.
The approach used in the study could serve as a screening method to analyze the effectiveness of new cancer therapies to determine, in advance, which cell populations are at risk during treatment.
