It is the commonest cancer in Britain, affecting 41,000 women a year – but not all breast cancers are the same. Yesterday, researchers said they had identified six types of the disease, with widely differing survival rates. The finding could help doctors give more accurate prognoses to patients, as well as targeting them with more specialised treatments.

Researchers at the University of Nottingham analysed 25 proteins present in the breast tissue of cancer patients and clustered them into groups according to how long the patients survived. They found two of the six groups had significantly longer survival and one had significantly shorter survival, while the remaining three fell between these extremes.

About 80 per cent of women diagnosed with breast cancer survive at least five years, with the best chance for those diagnosed early. There are clearly established treatments for each of the six types, based on hormonal therapy, treatment with the new drug Herceptin or aggressive chemotherapy. But these accounted for only 60 per cent of the 1,076 cases of breast cancer analysed.

The other 40 per cent of cases could not be classified into one of the six types and the treatment strategy in these cases was less clear, the researchers said.

Andy Green, senior research fellow at the University of Nottingham, who presented the findings to the National Cancer Research Institute's annual conference in Birmingham yesterday, said: "We are very excited by this research. We know breast cancers are very variable and one of our aims is to use clinical techniques to distinguish between them. It is the 40 per cent of breast cancers that we found to be unclassifiable that are the problem because we don't know what the optimal treatment strategy is for these cancers. It is a bit hit and miss at the moment."

The best survival was among women with oestrogen-positive breast cancer, which accounted for three of the six types, where up to 90 per cent of women survived 10 years. The poorest survival was women with HER2-positive breast cancer where 30 per cent died within four years.

Dr Green said the research was conducted before the advent of Herceptin, the breast cancer drug targeted at HER2 positive cancers, which was licensed and approved for use on the NHS in patients with early breast cancer last year. "I am sure some, but not all, women treated with Herceptin will have benefited from it," he said.

In another study at the conference, scientists from the University of Leicester said they had identified two genes which could cause severe side-effects in breast cancer patients treated with radiotherapy. Paul Symonds, who led the research published in the British Journal of Cancer, said radiotherapy was important but could be devastating when it went wrong. "Patients can get redness of the skin which may peel off. Later the breast may shrink and tissues under the skin may become hard and thickened [fibrosis]. Red, widened blood vessels can appear on the skin."

With the discovery it might be possible to predict which women would react badly and offer them alternatives. About 8 per cent of women carry the fibrosis gene and have 15 times the risk of developing thickening of the skin which can lead to chronic pain, he said.

In other research, University of Manchester scientists said they had identified a gene that triggers breast cancer stem cells, which can result in recurrence. Robert Clarke said a treatment already licensed for Alzheimer's disease had been shown to be effective against the gene.

Forms of the disease

* Luminal group – 40 per cent of total (three types). These are oestrogen-positive and respond to hormonal treatment (Tamoxifen and newer aromatase inhibitors). Two of the three have the best survival rates with 90 per cent of women living at least 10 years. The third is not as good.

* Basal group – 13 per cent (two types). These tend to be more aggressive and need a more aggressive response. They are treated with high-dose chemotherapy.

* HER2 positive – 7 per cent (one type). This has the poorest prognosis – 30 per cent of patients died within four years, before the introduction of the new drug Herceptin.

* Unclassified – 40 per cent. These cases are the hardest to treat because the best treatment is unknown.