The largest-ever study of breast cancer genomes has uncovered five new genes associated with the disease and 13 new mutational signatures that influence tumor development.  The new insight gives scientists a near complete picture of the events that cause the disease.  The information could lead to targeted, personalized treatments.

"This has implications for other types of cancer, too," said Professor Sir Mike Stratton, Director of the UK's Wellcome Trust Sanger Institute.  "The study itself shows it is possible to sequence individual cancer genomes and this should lead to benefits for patients in the long term."

Two reports appear in the journals Nature and Nature Communications.  Researchers sequenced the genomes of 560 breast cancers from people around the world and discovered five new genes that may spur breast cells to turn into breast cancer cells.  This is significant because each patient's cancer genome contains a complete historical account of the genetic changes that person has acquired throughout life.  Whatever damage occurs, by normal wear and tear or by exposure to bad things in the environment, it leaves a signature that can be detected - and that gives researchers clues about the causes of cancer.

"We can pull all this data together - the genes and the mutation patterns in each patient - to determine the personalized genomic profile of each cancer patient and through comparing and contrasting these patients, learn a lot about individual patient cancers," said lead study author Dr. Serena Nik-Zainal of the Sanger Institute.

Targeted therapies for many patients are a possibility because 60 percent of the mutations driving cancer are found in just 10 genes.  But the study also found that there are mutations so rare they are in just a tiny fraction of cancers.  That means it is unlikely that big pharmaceutical companies will have any financial incentive to develop therapies.