Breast cancer rules rewritten in ‘landmark’ study
What we currently call breast cancer should be thought of as 10 completely separate diseases, according to an international study which has been described as a “landmark”.
The categories could improve treatment by tailoring drugs for a patient’s exact type of breast cancer and help predict survival more accurately.
The study in Nature analysed breast cancers from 2,000 women.
It will take at least three years for the findings to be used in hospitals.
Cancer cartography
Researchers compared breast cancer to a map of the world. They said tests currently used in hospitals were quite broad, splitting breast cancer up into the equivalent of continents.
The latest findings give the breast cancer map far more detail, allowing you to find individual “countries”.
“Breast cancer is not one disease, but 10 different diseases,” said lead researcher Prof Carlos Caldas.
Analysis: What does this mean for patients?
The potential here is huge and it could have a transformative role in breast cancer care. However, we are a long way from using the new definitions in hospitals and the immediate impact on patients will be limited.
There are clear survival differences among the 10 categories. Clusters two and five seem to have a 15-year survival of around 40%. Clusters three and four have around 75% survival over the same period. This could help better inform patients.
In terms of treatments, there is bad news. There is a targeted therapy for just one of the 10 breast cancers groups. That is Herceptin, which is already used in a targeted group of patients. Other groups will still have “standard” therapies such as chemotherapy or radiotherapy.
The hope is that by identifying the 10 breast cancers it will be possible for researchers to design drugs for each one, but that is still a work in progress.
He added: “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.”
At the moment, breast cancers are classified by what they look like under the microscope and tests for “markers” on the tumours.
Imaging techniques play an important role in helping perform breast biopsies, especially of abnormal areas that cannot be felt but can be seen on a conventional mammogram or with ultrasound. One type of needle biopsy, the stereotactic-guided biopsy, involves the precise location of the abnormal area in three dimensions using conventional mammography.
Stereotactic refers to the use of a computer and scanning devices to create three-dimensional images. A needle is then inserted into the breast and a tissue sample is obtained. Additional samples can be obtained by moving the needle within the abnormal area.
Another type of needle biopsy uses a different system, known as the Mammotome breast biopsy system. The FDA (Food and Drug Administration) approved Mammotome in 1996; the hand-held version of the Mammotome received FDA clearance in September 1999. A large needle is inserted into the suspicious area using ultrasound or stereotactic guidance. The Mammotome is then used to gently vacuum tissue from the suspicious area. Additional tissue samples can be obtained by rotating the needle. This procedure can be performed with the patient lying on her stomach on a table. If the hand-held device is used, the patient may lie on her back or in a seated position.
There have been no reports of serious complications resulting from the Mammotome breast biopsy system. Women interested in this procedure should talk with their doctor.
Those with “oestrogen receptors” should respond to hormone therapies such as tamoxifen; those with a “Her2 receptor” can be treated with Herceptin.
The vast majority of breast cancers, more than 70%, should respond to hormone therapies. However, their reaction to treatment varies wildly. Prof Caldas said: “Some do well, some do horribly. Clearly we need better classification.”
Unprecedented scale
His team looked at frozen breast cancer samples from 2,000 women at hospitals in the UK and Canada.
They looked in huge detail at the genetics of the tumour cells - which genes had been mutated, which genes were working in overdrive, which were being shut down.
The study, by researchers in the UK and Canada, showed that all the different ways the cells changed when they became cancerous could be grouped into 10 different categories - named IntClust one to 10.
Prof Caldas said this was a “completely new way of looking at breast cancer”.
The study was funded by Cancer Research UK. Its chief executive, Dr Harpal Kumar, said: “This is the largest ever study looking in detail at the genetics of breast tumours.