A NETWORK of genes that help breast cancer to spread to the lungs has been identified in a study that could lead to better ways of diagnosing and treating the disease.

Research in the United States has revealed a set of genetic changes that not only predicts whether a breast tumour will move to the lungs, but also appears to play a critical role in the process.

The findings suggest that testing breast cancers for this particular constellation of genes could be used to provide more accurate prognoses and help to decide on the most suitable treatment. If a tumour is known to be likely to spread — or metastasise — to other parts of the body, a mastectomy is often appropriate. If the risk is less severe, a lumpectomy can be performed with greater confidence.

Early indications suggest that the genes not only indicate metastatic breast cancer, but enable fragments of tumours to break off and trigger the growth of fresh ones in the lungs.

Scientists at the Memorial Sloan-Kettering Cancer Centre in New York, who made the discovery, had already identified a series of genes that influence whether breast cancers will spread to a patient’s bones. Their second success, the details of which are published today in the journal Nature, has renewed optimism that it may eventually be possible to extend the technique to other forms of cancer.

The team, led by Joan Massagué, took cancer cells from a patient with an aggressive and metastatic breast tumour and transplanted them into mice. They then selected the cells that migrated to the animals’ lungs, and screened them for genetic changes.

The results were used to draw up a “metastasis signature” of genetic changes that are more common in cancer cells that move to the lungs. When tumours taken from breast cancer patients were examined for this genetic signature, it was found in those tumours that had spread to the lungs, indicating that it had played a part in the process.

Dr Massagué said: “Our work shows that the ability of a tumour to form metastases depends on the combined action of multiple genes — and a different set of genes is required for each organ the tumour spreads to.”

He added that there were drugs already available that targeted some of the genes. He said: “If you can successfully target these genes with a drug, you are helping to slow the growth of any primary tumour and also blocking the growth of any tumour cells that have spread to the lungs.”

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