Genetic test on breast cancer tissue may help some women avoid chemotherapy

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8 December 2015

A study of a 21-gene test carried out on tumour tissue removed from women with certain types of breast cancer found that it can accurately predict those who will do well with hormone treatment, without the need for chemotherapy.

The test, called Oncotype DX (Genomic Health Inc), measures the expression of 21 genes in paraffin-embedded sections of tumour, and provides the result as a risk of recurrence of breast cancer on a scale from 1 to 100, 1 being the lowest risk. It has been ‘sold as a service’ from the manufacturer’s US accredited laboratory for some years. The test was recommended by the National Institute for Health and Care Excellence (NICE) in September 2013 (after confidential agreement about provision to NHS organisations) to help make decisions about chemotherapy for breast cancer. The recommendation was largely based on retrospective studies comparing clinical outcomes with tests on stored tumours. NICE commented that retrospective studies are associated with increased bias compared with prospective randomised controlled trials.

The first results of an ongoing large multicentre prospective trial of Oncotype DX were published in the New England Journal of Medicine on 19 November 2015. The study involves 10,253 women aged 18 to 75 with early breast cancer whose tumours were hormone receptor positive (likely to respond to hormone treatment) and HER-2 negative (so unlikely to be aggressive) and who had no spread of tumour to glands in the armpit. All patients had tumours that were large or high grade under the microscope or both, and so met established guidelines for chemotherapy.

The women were divided into three groups based on their 21-gene test scores. Those with low predicted risk of recurrence scores of 1 to 10 were assigned to hormone treatment only, those with intermediate values of 11 to 25 were randomly assigned hormone treatment plus chemotherapy or hormone treatment only, and those with high risk values over 25 were assigned both treatments. The research is funded by the US National Cancer Institute and others.

The early New England Journal of Medicine report is limited to 1,626 women, 16% of the total, who were predicted to be at low risk and received only endocrine treatment. After five years 98.7% were free from recurrence of breast cancer and 99.3% were free from recurrence of breast cancer at a distant site (metastatic disease). Lead author Professor Joseph A. Sparano commented that the findings provide the highest level of evidence supporting expert-derived clinical practice guidelines which have recommended Oncotype DX in patients with early stage hormone receptor-positive breast cancer.

The results of the prospective randomised controlled trial in the intermediate group of women will be of the greatest clinical importance and are awaited with interest. As mandated by the study protocol, the data safety monitoring board of the trial continues to monitor outcomes in these patients.