SAN ANTONIO — A commercially available genetic assay has proved to be a potent predictor of the risk of local and regional recurrence of breast cancer, Dr. Terry Mamounas reported at a breast cancer symposium sponsored by the Cancer Therapy and Research Center.
The predictive power of the Genomic Health 21-gene expression assay known as Oncotype DX with regard to local and regional cancer recurrence in women with lymph node-negative, estrogen receptor-positive early breast cancer turned out to be similar to that demonstrated for distant recurrence risk in an earlier large clinical validation study (N. Engl. J. Med. 2004;351:2817–26), added Dr. Mamounas, chair of the National Surgical Adjuvant Breast and Bowel Project (NSABP) breast committee and medical director of the Aultman Cancer Center, Canton, Ohio.
“These results expand the predictive value of Oncotype DX and could have clinical implications for the individualizing of locoregional therapy decisions,” he said.
That proved to be the case in a separate study presented at the meeting by Dr. Ruth Oratz of New York University. She reported that knowledge of the recurrence risk based upon the gene expression test results caused four oncologists to alter their adjuvant therapy approach in one-quarter of 68 breast cancer patients.
The test results led to 3 patients being switched from planned adjuvant hormone therapy to chemotherapy, and 14 others who had been selected for chemotherapy being switched to hormone therapy. The investigator-sponsored study was conducted while Dr. Oratz was at the Rocky Mountain Cancer Center in Denver.
The polymerase chain reaction-based Oncotype DX assay measures expression of 5 reference genes and 16 cancer genes that reflect the tumor's proliferation, invasion, and HER2 and estrogen receptor status.
Dr. Mamounas reported on the results of Oncotype DX testing in tumor samples obtained from 1,674 breast cancer patients in the previously reported NSABP B-14 and B-20 randomized clinical trials. In 895 tamoxifen-treated patients, the 10-year locoregional recurrence rate was 4.3% in the 473 women with a low-risk Oncotype DX score, 7.2% in the 194 with an intermediate score, and 15.8% in the 228 patients with a high-risk score. The gene expression assay also was a significant predictor of locoregional recurrence in the 424 women who received adjuvant chemotherapy plus tamoxifen—although their 10-year event rate was only one-half that of women treated with tamoxifen alone—as well as in placebo-treated patients.
In a multivariate analysis, the Oncotype DX recurrence score was a significant predictor of locoregional recurrence conferring a more than twofold higher risk independent of patient age and tumor size or grade.
Dr. Mamounas and Dr. Oratz are on the speakers' bureau for Genomic Health.
These results expand the predictive value of Oncotype DX and could affect therapy decisions. DR. MAMOUNAS