Breast cancer DNA test may help patients avoid unnecessary chemotherapy

A genetic test could be used to spare breast cancer patients from having to undergo post-operative chemotherapy.

Doctors presented a study using the test, called Mammaprint, at the European Breast Cancer Conference in Vienna, Austria. The results suggest that it can accurately predict which patients' cancer is likely to spread (metastasise), thereby identifying ideal candidates for chemotherapy. Equally, Mammaprint can identify patients whose cancers will not spread - and therefore will not need further treatment after surgery - sparing them the serious side effects of aggressive drug treatment.

'It is encouraging to be able to tell patients we believe they will have just a good a chance of avoiding the recurrence of cancer by not having adjuvant chemotherapy as by having it', said Dr Sabine Linn, Associate Professor of Medical Oncology at The Netherlands Cancer Institute in Amsterdam. The goal of adjuvant chemotherapy is to ensure any cancerous cells that might remain after surgery are destroyed.

In their study, Dr Linn and team used genetic data from 427 breast cancer patients whose cancer had not yet spread to their lymph nodes. Mammaprint looks for a particular set of 70 genes in tumour tissue, and of the 219 women in the study who were determined to be at low risk of metastasis, only 15 percent underwent adjuvant chemotherapy. Despite this low number, the women had a five-year disease-free survival rate of 96 percent, compared with 90 percent among the women who had been identified as high risk and who had undergone chemotherapy.

'Based on our data, the use of the genomic test could lead to a reduction of nearly 30 percent in the use of adjuvant chemotherapy without compromising patient outcomes', said Dr Linn, who added that the figure could nonetheless vary by country. 'Many patients dread the idea of chemotherapy, and by avoiding it they can substantially reduce the stress involved in having cancer, as well as improve their overall quality of life,' she added.

In another study presented at the conference, Belgian researchers explained that genetic testing could also be used to identify which breast cancer patients are most likely to suffer life-threatening effects of chemotherapy. Their study showed that of 1,100 women treated with common chemotherapy drugs, 17 percent were hospitalised with such effects, and 15 percent possessed associated genetic variants.

Dr Christof Vulsteke from the Catholic University in Leuven said that investigating patients' genetic makeup before beginning chemotherapy would allow doctors to 'support the patient with either growth factors to increase the patient's immunity, or dose modification, or a different chemotherapy regimen better adapted to the patient'.