A new test may help breast cancer patients and their doctors determine the likelihood that the cancer will recur. If relapse is unlikely, these women could potentially avoid follow-up treatment, which is often associated with side effects that occasionally can be substantial. The multi-gene assay, called Oncotype DX ™, is a genomic test that examines the activity of 21 genes to quantify the likelihood of recurrence among women with early stage breast cancer.

Published in an advance online issue of The New England Journal of Medicine (NEJM) on December 10, 2004, the validation study examined the ability of the test to predict recurrence using tissue samples from 668 patients with node-negative, estrogen receptor-positive breast cancer treated with tamoxifen. The assay accurately assigned patients into high and low risk groups based on actual recurrence rates and proved to be a better predictor than usual measures, including patient’s age, tumor size, and tumor grade. This information may help doctors tailor the most appropriate, individualized treatment plans for their breast cancer patients.

The study’s findings were published to coincide with results presented at the 27th Annual San Antonio Breast Cancer Symposium from another study examining the utility of chemotherapy in treating newly diagnosed patients with breast cancer. This study of 651 women with early stage breast cancer treated with either tamoxifen alone or tamoxifen plus additional chemotherapy found that those who had high risk of recurrence based on the Oncotype DX also benefited the most from chemotherapy, measured as distant recurrence-free survival after 10 years. Likewise, those who had Oncotype DX scores indicating low risk of recurrence responded the least. The researchers suggest that Oncotype DX could become an important tool in treatment evaluation of breast cancer patients and may help some patients avoid side affects from potentially unnecessary chemotherapy.

While this test is commercially available, many professionals would like to see further validation. In addition, some caution against using this test in clinical decision making at this time. According to these professionals, further studies are needed to confirm that withholding therapy in "low risk" women does not increase their chances of disease recurrence. It is also important to emphasize that this panel of genetic markers has only been studied in patients treated with tamoxifen. Future applicability of the test to breast cancer patients whose oncologists opt to treat them with drugs other than tamoxifen has yet to be shown. Nevertheless, Oncotype DX does represent a positive step toward more individualized care of cancer patients through the laboratory’s growing ability to help direct specific therapies based on genomics.

Sources
S. Paik et al. Multigene Assay to Predict Recurrence of Tamoxifen-Treated, Node-Negative Breast Cancer. New England Journal of Medicine. Published online December 10, 2004. Abstract available at: http://content.nejm.org/cgi/content/abstract/NEJMoa041588

New York Biotechnology Association. News Room: The National Surgical Adjuvant Breast and Bowel Project (NSABP) and Genomic Health, Inc. Announce Positive Study Results Demonstrating Oncotype DX Genomic Breast Cancer Assay Predicts Chemotherapy Response, December 10, 2004

Cancer Consultants. Breast Cancer News: New Test May Help Define Good and Poor Prognosis in Breast Cancer.

27th Annual San Antonio Breast Cancer Symposium. Abstract [24]: Expression of the 21 genes in the Recurrence Score assay and prediction of clinical benefit from tamoxifen in NSABP study B-14 and chemotherapy in NSABP study B-20. Paik S, Shak S, Tang G, Kim C, Joo H, Baker J, Cronin M, Watson D, Bryant J, Costantino J, Wolmark N. Presented December 10, 2004. Abstract available online at: http://www.abstracts2view.com/sabcs/sessionindex.php (Search “oncotype”)

Stein, Rob. Breast Cancer Test Tells If Recurrence Is Unlikely. Washington Post, December 11, 2004; A1, A12.