The findings of a new Dutch study could help to identify breast cancer patients who are likely to respond to treatment using Herceptin.
Almost half of patients do not improve when treated with Herceptin.
The researchers found that a tumour suppressor called PTEN and mutations of the PIK3CA gene could be used as biomarkers to predict treatment response.
They found that both PTEN expression and PIK3CA mutation is required for optimal prediction of disease progression.
Senior author Dr Rene Bernards said: "It is too early to use these biomarkers; further validation studies are required before they can be used in the clinic.
"Nevertheless, it is likely that these findings will lead to a better understanding of resistance mechanisms and how to circumvent them as well as more reliable identification of the most effective treatment for individual patients."
The research appears in the October issue of Cancer Cell.
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