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.

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, including researchers at The Institute of Cancer Research, London, The Royal Marsden NHS Foundation Trust, and University College London Hospitals NHS Foundation Trust, led internationally by researchers at Garvan Institute of Medical Research in 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 tumour types - p53, APC, BRCA1 and BRCA2 -- putting these patients at increased risk of other cancers such as breast, ovarian or bowel cancer.

When such mutations are found, families can be offered genetic counselling and screening, where appropriate.

The new research, published in The Lancet Oncology, also found that 19 percent 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.

Researchers initially targeted their efforts to analyse the DNA sequence of 72 genes linked to increased cancer risk in 1,162 sarcoma patients aged over 15 years.

Some 55 percent of patients in the study harboured potentially harmful mutations in at least of one of the 72 genes tested.

Inherited mutations in the genes BRCA2, ATM, ATR and ERCC2 were found to be common in sarcoma patients, and linked to risk of sarcoma for the first time by this study.

A fifth of the patients had mutations in more than one of the genes tested and, importantly, people with genetic errors in multiple cancer genes were found to be more likely to get cancer at a younger age than those with a single genetic mutation.

This is the first evidence that multiple genetic mutations interacting could be causing sarcomas in some patients, rather than a single gene driving their disease.

The UK arm of the project involves 250 patients and is being led by researchers at The Institute of Cancer Research (ICR) and The Royal Marsden, supported by Sarcoma UK and the Liddy Shriver Sarcoma Initiative.

It is part of a worldwide research project called the International Sarcoma Kindred Study (ISKS), being led by researchers at the Garvan Institute of Medical Research in Australia and will include colleagues in the UK, US, France, India and New Zealand.

Current UK project leader Professor Winette van der Graaf, Professor of Personalised Oncology at The Institute of Cancer Research, London, and Consultant at The Royal Marsden NHS Foundation Trust, said "This study gives us the most detailed picture yet of the genetics of sarcoma patients, and reveals that in a significant proportion there may be a genetic cause for this rare cancer, and other, more common types of the disease. The research helps explain why some patients with sarcoma are prone to develop other cancers in their lifetime, and provides new clues to the phenomenon of 'cancer families'."

"This collaborative work also suggests that much of inherited cancer predisposition may be due to defects in multiple genes working together, any one of which would be unlikely to cause cancer on its own. It's an important step forward in our understanding of sarcoma genetics, and is just the first part of a much bigger research project to catalogue many more contributors to cancer risk."

Study co-author Professor Ian Judson, who led the UK arm of the study at The Institute of Cancer Research, London, and The Royal Marsden, said "Sarcomas are rare types of cancer that disproportionately affect the young, have low survival rates and in which there are currently few treatment options available. This important study has uncovered mutations occurring in some sarcoma patients that could potentially be targeted by precision treatments -- opening up new avenues for treatment that should be investigated in clinical trials. It's also fascinating that this study has shed light on the inheritance of cancer risk in families more widely, and offers clues to explaining why some families are affected by many different cancer types."

Sarah McDonald, Director of Research at Sarcoma UK, said "Sarcoma UK supports high quality research; this project has provided evidence around the inherited risks of sarcoma and cancer. If we can identify individuals at high risk of developing sarcomas this could lead to earlier detection and more effective treatment of these tumours. With 10 people every day diagnosed with sarcoma in the UK, Sarcoma UK is delighted to support the UK recruitment of participants into of this study. We looking forward to hearing Professor David Thomas from the international project team giving the Keynote address at Sarcoma UK's Research Symposium this autumn."