At least 2% of people over the age of 40 and 5% over age 70 have mutations linked to leukemia and lymphoma, according to research published in Nature Medicine.
The findings, based on blood samples from nearly 3000 patients, don’t necessarily mean that people with these mutations will develop leukemia or lymphoma.
They may have a higher-than-normal risk of developing these malignancies, but more research is needed to determine the risk.
“We would not want anyone to think they should be screened for these mutations to understand their risk of leukemia or lymphoma,” said Timothy Ley, MD, of the Washington University School of Medicine in St Louis, Missouri.
“The ability to understand how mutations in these genes increase a person’s risk of blood cancers is a long way off, and genetic testing would be of no benefit at this time.”
Dr Ley and his colleagues analyzed blood samples from people enrolled in The Cancer Genome Atlas project. The patients had been diagnosed with cancer but were not known to have leukemia, lymphoma, or a blood disease.
They ranged in age from 10 to 90 at the time of diagnosis and had donated blood and tumor samples before starting cancer treatment. Therefore, any mutations the researchers identified would not have been associated with chemotherapy or radiation.
The team looked closely at 556 known cancer genes. In 341 patients ages 40 to 49, fewer than 1% had mutations in 19 leukemia- or lymphoma-related genes.
But among 475 people ages 70 to 79, more than 5% did. And more than 6% of the 132 people ages 80 to 89 had mutations in these genes.
The researchers noted that 9 of the 19 genes were mutated repeatedly, an indicator that the changes drive or initiate the expansion of blood cells.
This expansion of cells is clearly not leukemia or lymphoma, the researchers said. It may be a precursor to hematologic malignancies in a small subset of patients, but the study was not designed to predict the future risk of developing these diseases.
The researchers also said this study likely underestimates the percentage of people with mutations in leukemia and lymphoma genes because the team was only able to identify small mutations, not large structural variations or the insertions and deletions of chunks of genetic material.
