Results from the biggest breast cancer tumour study ever conducted could revolutionise the way the disease is diagnosed and treated, it has been claimed.
Scientists reclassified breast cancers into 10 completely new categories based on their genetic "fingerprints".
Several entirely new breast cancer genes that drive the disease were also uncovered. The wealth of new data is expected to lead to better ways of predicting patient survival, as well as novel treatments tailored to people's genetic make-up.
The research, published in the journal Nature, is the largest ever global study of breast cancer tissue. It marks the culmination of decades of work by British and Canadian scientists led by a Cancer Research UK team based in Cambridge.
Genetic material from 2,000 tumour samples taken from women diagnosed with breast cancer between five and 10 years ago was analysed in the study. The scientists sorted the samples into 10 subtypes based on common genetic features linked to survival. The new classification has major implications for drug treatment, paving the way to more personalised therapies. All the breast cancer genes identified by the scientists are potential targets for the development of new drugs.
Links between these genes and known cell signalling pathways - the networks that control cancer growth - were also revealed. This will make it easier to pinpoint how the faulty genes cause cancer.
Professor Carlos Caldas, senior group leader at Cancer Research UK's Cambridge Research Institute, said: "Our results will pave the way for doctors in the future to diagnose the type of breast cancer a woman has, the types of drugs that will work, and those that won't, in a much more precise way than is currently possible.
"This research won't affect women diagnosed with breast cancer today. But in the future, breast cancer patients will receive treatment targeted to the genetic fingerprint of their tumour.
"We've drilled down into the fundamental detail of the biological causes of breast cancer in a comprehensive genetic study. Based on our results we've reclassified breast cancer into 10 types - making breast cancer an umbrella term for an even greater number of diseases. Essentially we've moved from knowing what a breast tumour looks like under a microscope to pinpointing its molecular anatomy - and eventually we'll know which drugs it will respond to."
The next stage is to discover how tumours in each subgroup behave - for instance, whether they grow or spread slowly or quickly, he said.