When one twin gets cancer, other faces higher risk

A new study of twins has found that having a twin sibling diagnosed with cancer poses an excess risk for the other twin to develop any form of cancer

Among the 23 different types of cancer studied, an excess familial risk was seen for almost all of the cancers, including common cancers such as breast and prostate cancer, but also more rare cancers such as testicular cancer, head and neck cancer, melanoma, ovarian and stomach cancer.

The study showed, for the first time, that in twin pairs where both developed cancer, each twin often developed a different type of cancer- which suggests that, in some families, there is a shared increased risk of any type of cancer.

The researchers looked at more than 200,000 twins, both identical and fraternal, in Denmark, Finland, Norway, and Sweden, who participated in the Nordic Twin Study of Cancer and were followed over an average of 32 years between 1943 and 2010.