Genomic Health Announces Study Establishing the Utility of Oncotype DX® in Node-Negative and Node-Positive Breast Cancer Patients Treated with Aromatase Inhibitors

Genomic Health, Inc. has announced findings from a European study, involving Professor Mitch Dowsett,  Royal Marsden Hospital and Team Leader at the Breakthrough Breast Cancer Research Centre in London, which demonstrated that the Oncotype DX Recurrence Score® result is a significant independent predictor of distant recurrence in both node-negative and node-positive, hormone receptor-positive breast cancer patients who are treated with the aromatase inhibitor anastrozole or with tamoxifen. The results were presented at the 31st Annual San Antonio Breast Cancer Symposium.

Oncotype DX is a multi-gene expression test that physicians currently use to predict the likelihood of chemotherapy benefit as well as the likelihood of recurrence for women with early stage breast cancer.  In this prospectively-designed study, researchers used Oncotype DX to analyze tumor samples from 1,231 patients in the ATAC (Arimidex®, Tamoxifen, Alone or in Combination) trial, a landmark study that established the wide use of aromatase inhibitors for adjuvant treatment of postmenopausal women with hormone receptor-positive breast cancer. 

“Our multivariate analysis confirms that along with other standard measures such as tumor size, Oncotype DX contributes independently to providing a more complete picture of prognosis,” said Mitch Dowsett, Ph.D., Royal Marsden Hospital and Team Leader at the Breakthrough Breast Cancer Research Centre in London. “Physicians can take this information into account when making chemotherapy treatment decisions for both node-negative and node-positive early stage breast cancer patients planned for either anastrozole or tamoxifen treatment.”

The study assessed 9-year distant recurrence for women in the anastrozole and tamoxifen monotherapy arms of the ATAC trial, including patients with disease that had spread to the lymph nodes (0 nodes, 1-3 nodes and more than 4 nodes).  Researchers, with support from the UK’s leading breast cancer charity, Breakthrough Breast Cancer, and AstraZeneca, collected tumor blocks, mainly from patients in the United Kingdom, and tested the significance of adding the Recurrence Score result to a clinical model consisting of age, tumor size, grade and treatment, as well as the Adjuvant! Online risk assessment tool.

The study indicated that the Oncotype DX Recurrence Score (RS) result showed statistically significant prognostic value beyond that provided by Adjuvant! Online in both node-negative (p<0.001) and node-positive (p=0.003) patients.  The greater efficacy of anastrozole observed in the parent ATAC trial and the similar hazard ratios for the RS in both treatment arms from this study suggests a lower risk of recurrence in patients treated with aromatase inhibitors. In addition, for any RS result, the likelihood of distant recurrence increases with the number of positive nodes.

“This study is the largest that Genomic Health has conducted to date, reinforcing our commitment to continue adding value to the Oncotype DX breast cancer assay by studying additional patient populations and treatment regimens relevant to current clinical practice,” said Steven Shak, M.D., chief medical officer of Genomic Health.  “These results, combined with the suite of clinical evidence that we and our clinical partners generated over the past five years, reinforce our belief that Oncotype DX is an indispensable tool when making treatment decisions for node-negative patients and in certain node-positive patients.”

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