Genetic testing of patients with a rare form of cancer that can affect children and young adults can pick out genetic errors hidden in their family tree which increase the risk of a wide variety of cancer types, a new study shows.

Cancer is such a common disease that it is no surprise that many families have at least a few members who have had cancer.  But some families seem to develop a disproportionately large number of cases of the disease.

Inherited cancer-causing mutations can give rise to the phenomenon of 'cancer families' where multiple family members develop cancer – sometimes one type, sometimes many different types of cancer, depending on the gene involved.

A team comprised of researchers from England and Australia looked at patients with rare cancers called sarcoma to shed light on the genetic causes of multiple cancers within families. They found that over half of 1,162 patients with sarcoma tested were born with mutations in at least one gene already known to increase cancer risk.

Some of the most common inherited mutations occurred in genes known to drive the development of multiple tumor types – p53, APC, BRCA1 and BRCA2 – putting these patients at increased risk of other cancers such as breast, ovarian or colon cancer. When such mutations are found, families can be offered genetic counseling and screening, where appropriate.

The new research, published in Lancet Oncology, also found that 19 per cent of the patients had mutations that could be targeted by new or existing cancer drugs and could point the way towards clinical trials in sarcoma patients.