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Scientists analyse breast cancer types

25th September 2012

Researchers in the United States have published findings that could reshape what is currently known about breast cancer.

breastcancer

The new, large-scale study builds on recent smaller studies which have divided breast cancer into four types which are genetically different from each other.

Genetic changes also seem to affect how these tumours differ from each other, even within the same type, and could pave the way for revolutionary new treatments.

Writing in the online edition of the journal Nature, the 348 researchers who carried out the US federal-government funded study, said that their findings could lead to certain types of breast cancer being treated with drugs that were developed to target other cancers.

It could also generate more precise treatments targeting genetic aberrations that currently have no treatment.

Study researcher Matthew Ellis said the study--the first comprehensive genetic analysis of breast cancer--had outlined a road map for how doctors might treat breast cancer in future.

More than 35,000 women die of breast cancer annually in the US alone.

However, new drugs and treatment options could still take years to develop, researchers warn.

Each of the four main types of breast cancer tumour is still highly individual in the way it is driven by genetic changes, although eventually doctors may be able to tailor medicines to individual tumours.

According to Karuna Jaggar, head of the advocacy group Breast Cancer Action, there are still many scientific hurdles to overcome before the study results can be translated into meaningful therapeutic options for breast cancer patients.

The study, which was based on an analysis of tumours from 825 patients, is part of a larger project known as the Cancer Genome Atlas, which aims to build maps of genetic changes in common cancers.

Similar studies of lung and colon cancer have also been published recently. Programme director Brad Ozenberger of the National Institutes of Health said the world had never before seen a breast cancer genomics project on such a large scale.

Possible drug targets for breast cancer could be found in at least 40 genetic alterations found in the tumours, giving experts a good view of what goes wrong in breast cancer, according to Oregon-based genetics expert Joe Gray.

The study aimed to pick up early genetic changes in the most common types of cancer that are believed to arise in the milk duct, in the hope of identifying treatment pathways before the cancers metastasised, or spread to other organs in the body.

In a surprise discovery, researchers found that a particularly deadly breast cancer that somewhat resembles the basal cells of the skin and sweat glands, known as a "triple negative," was very different from any other type of breast cancer, and was genetically much closer to ovarian cancer and a particular type of lung cancer.

According to study co-author James Ingle of the Mayo Clinic, the discovery raises the possibility of a common cause for the three cancers.

Experts say some of the findings could soon translate into different treatment approaches using existing drugs. For example, triple negative breast tumours could be treated with a drug now used to target ovarian cancer.

This would give some breast cancer patients a good reason to avoid anthracyclines, dreaded by breast cancer patients because they are associated with heart damage and leukaemia.

Ellis said that a new type of drug, PARP inhibitors, could be tried in such tumours, which are most prevalent in younger women, in African-Americans and in women with breast cancer genes BRCA1 and BRCA2.

The genetic analysis divided into two types the sort of tumours that arise in the cells lining milk ducts, suggesting that only one type of tumour would need chemotherapy, while the other might respond to hormonal therapy to block oestrogen from spurring tumour growth.

According to study lead author Charles Perou of the University of North Carolina, one "stunning" finding was that genetic aberrations seemed to actually cause the tumours in the first place, suggesting that the research was getting "close to the root" of some cancers.

The analysis also found that not all HER2-enriched tumours are the same, suggesting that only some would benefit from the expensive and not always well-tolerated drug Herceptin. Clinical trials are currently being planned to test this approach.

Many more studies will be needed to focus in closely on each different genetic change.


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