Family colon cancer risk similar for siblings and half-siblings

Siblings of people with colorectal cancer are at higher risk for the disease, but a new study suggests half-siblings face nearly the same risk.

In the BMJ research, siblings of colorectal cancer patients had a 7% cumulative lifetime risk of developing the tumours, which is 1.7 times the risk of colorectal cancer for people without any family history of these tumours.

Half-siblings of colorectal cancer patients had a 6% cumulative lifetime risk — which is 1.5 times the risk without a family history.

Researchers analysed data on more than 16 million people living in Sweden from 1958 to 2015.

Among people with clear genealogy records, 173,796 developed colorectal cancer.

"We showed that family history of colorectal cancer in a half-sibling (with no other affected first- or second-degree relative) has a much stronger association with increased risk of colorectal