"The relationship to total response was remarkable," says Professor von Minckwitz. "Tumours with a high level of PARP expression had a total response in 26% of cases, whereas those tumours which did not express PARP had a total response in only 9%. Additionally, we found that the presence of PARP can provide more accurate prognostic information than the grade of differentiation or degree of abnormality of tumours. We believe that this is the first study to describe a broad expression of PARP in untreated breast tumours together with a correlation of sensitivity to chemotherapy."

PARP positive tumours could become a new entity in breast cancer, the investigators say. They intend to follow up their initial findings by a trial randomising patients to either chemotherapy alone or chemotherapy plus a PARP inhibitor. "Particularly in triple-negative tumours there is a great need to improve treatment options," says Professor von Minckwitz. "Apart from chemotherapy, there is no other treatment such as endocrine or anti-HER2 therapy available for this aggressive form of breast cancer."

However, it remains to be seen whether immunohistochemical detection (the process of localising antigens in tissue cells) of PARP is the best method of predicting PARP inhibitor efficacy, the scientists say. "We need more prospective trials to be sure that there is no better way of making sure that the right people are getting the right therapy," says Professor von Minckwitz. "However, it would be fair to say that we believe that we may be on the verge of a major change in the way breast cancer is treated."

Source German Breast Group Forschungs GmBH