Results from the TAILORx Trial – MAC.12 (ECOG PACCT-1)

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Thursday, October 9, 2014

The first results from the TAILORx Trial – MAC.12 – just published in the New England Journal of Medicine, are part of the larger Canadian Cancer Trials Group MAC.12 (ECOG PACCT-1) trial – Program for Assessment of Clinical Cancer Tests (PACCT-1): Trial Assigning Individualized Options for Treatment (TAILORx). This study was designed to further validate and refine the clinical usefulness of the 21-gene assay (Oncotype DX Recurrence Score, Genomic Health) in women with hormone-receptor–positive, HER2-negative, axillary node-negative invasive breast cancer.  Women were categorized into three groups based on their recurrence score. These initial results report on the outcomes of women who had recurrence scores of 0-10 and who were assigned to receive endocrine therapy alone without chemotherapy.

Of the 10,253 eligible women enrolled onto MAC.12, 1626 women (15.9%) had a recurrence score of 0 to 10 and were assigned to receive only endocrine therapy. At 5 years, the rate of invasive disease-free survival was 93.8% (95% confidence interval [CI], 92.4 to 94.9), the rate of freedom from recurrence of breast cancer at a distant site was 99.3% (95% CI, 98.7 to 99.6), the rate of freedom from recurrence of breast cancer at a distant or local-regional site was 98.7% (95% CI, 97.9 to 99.2), and the rate of overall survival was 98.0% (95% CI, 97.1 to 98.6). The rate of recurrence of breast cancer at a distant site was less than 1% and the risk of any recurrence was less than 2% at 5 years.

The majority of women with early-stage breast cancer are advised to receive chemotherapy in addition to radiation and hormonal therapy. These results suggest that the use of a molecular profiling test, in this case Oncotype Dx, can be used in clinical decision-making and safely spare some women unnecessary chemotherapy and the associated side effects.

The trial was conducted in Canada by the Canadian Cancer Trials Group and included the participation of 24 Canadian centres who randomized a total of 838 patients onto the entire trial.

Dr. Kathleen Pritchard, Canadian Chair of MAC.12, medical oncologist at Sunnybrook Health Sciences Centre, and past Chair of the Canadian Cancer Trials Group’s Breast Site Committee, was interviewed on CTV news to discuss the trial results. You can watch Dr. Pritchard here.

The results were published in the New England Journal of Medicine, on September 27, 2015. A link to the article is provided here.

Congratulations and thanks to all participating centres and staff for their efforts in making this trial a success, and to all those women who volunteered to participate.