More breast cancer patients could benefit from treatments currently used only for patients with a faulty BRCA1 or BRCA2 gene, an international research collaboration has shown.

Dr Peter Simpson and Professor Sunil Lakhani from The University of Queensland’s Centre for Clinical Research (UQCCR) were part of the team which sequenced every gene mutation in 560 breast cancer tumours.

Dr Simpson said the research showed that almost 22 per cent of breast tumours had a genetic signature reflecting a BRCA deficiency, even though the patient had not always inherited a mutation in one of the two genes.

“BRCA genes are DNA repair genes, so if there is a fault or mutation in one of these genes there is more susceptibility for a patient to develop a disease such a breast cancer,” Dr Simpson said.

“Between one and five per cent of breast cancer cases are due to inherited BRCA1 or BRCA2 mutations.”

The researchers developed a computer program to identify tumours with a BRCA deficiency, based on the appearance of the genome.

Professor Lakhani said the tool could be incredibly useful from a treatment point of view, because if a patient had this type of DNA repair deficiency, it opened up the possibility that the tumour would be responsive to a particular type of drug called PARP inhibitors.

“These PARP inhibitor drugs are currently in clinical trials where most of the focus is on patients with a genetic deficiency in BRCA1/BRCA2,” Professor Lakhani said.

“This study has identified a much larger patient group who could benefit.

“It could be an effective way of picking those patients where particular treatments are going to work, and that’s a big step forward in cancer research.”

Dr Simpson and Professor Lakhani worked on the collaboration led by the Wellcome Trust Sanger Institute with Pathology Queensland and the Royal Brisbane and Women’s Hospital to provide patient tissue samples and pathology analysis for the study.

The research was published in the journal Nature Medicine.