Scientists have discovered a rare genetic fault that raises a woman's risk of developing ovarian cancer six-fold. It has been hailed as the most important discovery in the field in the last ten years, and offers hope for new treatments.

'This landmark discovery is another piece of the jigsaw deepening our understanding of the disease. We hope this will have a significant impact in providing more personalised treatments for patients based on their genetic make-up', said Harpal Kumar, chief executive of Cancer Research UK, who funded the project.

The team, from the UK's Institute of Cancer Research, compared the genomes of more than 900 families affected by breast and ovarian cancers with more than 1000 controls. They found eight mutations in one gene, called RAD51D, which is known to be involved in DNA repair.

Ovarian cancer is the fifth most common cancer worldwide, and affects around 6,500 women in the UK each year. It can develop without displaying clear symptoms and is often only discovered when the cancer has spread elsewhere. Due to this fact up to 70 percent of patients die within five years of diagnosis.

The risk of developing ovarian cancer increases from one in 70 women, to one in 11 if they have a faulty RAD51D. 'At this level of risk, women may wish to consider having their ovaries removed after having children to prevent ovarian cancer occurring', said study author Professor Nazneed Rahman.

He continued: 'There is also hope on the horizon that drugs specifically targeted to the gene will be available'. The discovery highlights the potential efficacy of a new class of anti-cancer drugs called PARP inhibitors. They are already showing promise in clinical trials for the treatment of breast and ovarian cancers related to mutations in the BRCA1 and BRCA2 genes, both of which also play a part in the DNA repair process.

'It's incredibly exciting to discover this high risk gene for ovarian cancer', said Professor Nic Jones, chief scientist at Cancer Research UK. 'We believe the results of this research will help inform personalised treatment approaches and give doctors better information about risks of cancer to tell patients'.

The study was published in the journal Nature Genetics.