Up to one-quarter of patients with colorectal cancer who have a family history of the disease could have the causes of their cancer identified through gene testing, a new study has reported.

Wider testing for known cancer genes in patients with colorectal cancer could help in their diagnosis and treatment, and in the early detection or prevention of cancers in their relatives, the researchers said.

Scientists at The Institute of Cancer Research, London, sequenced genes of more than 600 patients with a family history of colorectal cancer. They found that known mutations could be identified in a high proportion of cases.

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The researchers, who received funding from Cancer Research UK and the European Union, said their findings suggested patients with colorectal cancer and a family history should routinely be tested for a range of known cancer genes.

But they stressed there was also a need for further research to identify new cancer genes that could be involved in the three-quarters of cases where no mutations in known cancer genes could be detected.

Scientists at The Institute of Cancer Research (ICR) sequenced the DNA of 626 patients with colorectal cancer and a family history of early-onset disease from 140 clinical centers across the United Kingdom.

Their study, published in the Journal of Clinical Oncology (2015; doi:10.1200/JCO.2014.56.5689), found that inherited susceptibility to colorectal cancer was common among patients with a family history of the disease.

Inherited mutations in the mismatch repair genes alone accounted for 11% of familial colorectal cancers. Genetic screening to detect defects in these genes has previously been shown to reduce colorectal cancer death rates.

“Knowing which cancer gene has caused bowel [colorectal] cancer isn’t just important for researchers—it’s crucial for the treatment, counselling, and surveillance of patients and their relatives,” said Professor Richard Houlston, MD, PHD, Professor of Molecular and Population Genetics at The Institute of Cancer Research, London.

“Our study has found that using just existing tests for known cancer genes, we could identify the genetic causes of familial bowel [colorectal] cancer in perhaps as many as a quarter of cases. It’s vital that we improve access to genetic testing for cancer patients and their relatives so as many as possible can have a genetic diagnosis.

“Of course, we are still left with three-quarters of patients where no genetic cause could be identified, and that underlines the need for further research to identify new cancer genes,” added Houlston.

“So far, there are 10 gene faults that we know are linked to inherited bowel [colorectal] cancer. People with these gene faults have a much higher risk of developing the disease and so are screened from a younger age. But this research shows that around three-quarters of people with a family history of bowel cancer do not have these known gene faults,” said Dr Áine McCarthy, science information officer at Cancer Research UK.

“By testing a much larger portion of their DNA we may be able to discover other mistakes in different genes that can also cause bowel cancer. This could potentially help doctors decide how best to monitor people for early signs of bowel cancer and guide their treatment.”