A new study has found that some chemotherapy drugs can cause more harm to healthy cells than others, possibly even making them look “older” at the genetic level.
Published in Nature Genetics, the study looked at how chemo affects healthy blood cells. Scientists found specific patterns of DNA damage, called mutational signatures, that were linked to certain chemotherapy drugs. These patterns show how much a drug may damage healthy cells, and four of them had never been seen before.
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Researchers studied blood samples from 23 people (aged 3 to 80) who had received chemotherapy and compared them with samples from nine people who hadn’t had cancer or chemotherapy. They discovered that some chemo drugs, like cyclophosphamide (used to treat cancers like breast cancer), caused far fewer mutations than others. This is important because more mutations in healthy cells can raise the risk of getting another cancer later, known as a secondary tumour.
The team, led by scientists from the Wellcome Sanger Institute and The Chinese University of Hong Kong, highlighted the case of a 3-year-old who had undergone chemo and had 10 times more DNA mutations than other kids his age. His blood cells even looked older than those of an 80-year-old who had never had chemo. While these changes don’t always lead to cancer, they increase the risk over time, just like ageing does.
Experts say chemo damages fast-dividing cells, which include both cancer cells and some healthy cells like those in the blood. The more damage there is, the higher the chance of long-term side effects.
One of the researchers, Dr Emily Mitchell, said they hope future studies can test this theory with larger groups.
