Scientists have identified genes enabling breast cancer cells to spread to the lungs, a discovery that could improve diagnosis and treatment of the disease.

The set of genes not only reveals where the cancer will spread, but also how virulent it is likely to be. The genes could be potential targets for existing or new breast cancer drugs, according to the researchers.

“We have looked for and found a specific set of genes that some breast cancers utilise to form metastasis to the lungs specifically,” Dr Joan Massague, of the Howard Hughes Medical Institute at the Memorial Sloan-Kettering Cancer Center in New York, said on Wednesday.

The lungs, with the bones, liver and brain, are the main organs to which breast cancer spreads. For each organ the cancer invades it needs a specific set of genes.

The findings reported in the science journal Nature are important because if breast cancer is diagnosed and treated early, women have a better chance of beating the disease.

After it has spread beyond the breast it is more deadly because treatments are less effective.

Breast cancer is one of the most common cancers in women worldwide. More than a million new cases occur each year, according to the International Agency for Research on Cancer in Lyon, France.

MEDIATORS FOR METASTASIS

The genes which can be found in some primary breast tumours seem to predict a high risk of spread to the lungs even years later.

The discovery could help doctors to identify women whose cancer is most likely to spread to the lungs so they can closely monitor them and try to block it, or treat it as early as possible.

Massague and his team discovered the pattern of gene activity by studying tumours from 82 patients whose breast cancer had spread to the lungs.

They analysed data from a similar group of patients from the Netherlands and found the same genetic signature.

Massague said the genes were not just markers for cancer spreading, but were also mediators that caused it to spread. The proteins they produced could become prime targets for existing or new drugs to prevent metastasis - the spread of cancer.

“Compounds already exist to block some of the genes we have identified or the cell function they regulate. The next step is to begin testing these compounds in animal models to see if they can block metastasis,” Massague said.

If someone is diagnosed with cancer and the tumour is found to have the genes, doctors may be able to provide drugs preventively, or at least have them ready for whenever the metastasis is detected.

The scientists believe the technique could be expanded to pinpoint genes involved in the spread of breast cancer to other organs or other types of cancer.

“We have already identified a set of genes that mediate metastasis to the bone,” said Massague.