NEW YORK (GenomeWeb News) - At the San Antonio Breast Cancer Symposium earlier this month, Genomic Health reported findings from a European study demonstrating that the Oncotype DX Recurrence Score result is an 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.
Oncotype DX is a multi-gene expression test that predicts the likelihood of chemotherapy benefit and breast cancer recurrence. The test is currently marketed to women with early-stage (Stage I or II), node-negative, estrogen receptor-positive invasive breast cancer who will be treated with hormone therapy.
In the prospectively designed study presented at SABCS, researchers used Oncotype DX to analyze tumor samples from 1,231 patients in the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial.
The study looked at nine-year distant recurrence for women whose disease had spread to the lymph nodes and were on anastrozole and tamoxifen monotherapy in the ATAC trial. The study was conducted by researchers at the Royal Marsden Hospital, and was supported by Breakthrough Breast Cancer, a leading breast cancer charity in the UK, and AstraZeneca. The partners collected tumor blocks mostly from patients in the UK and assessed the impact on patient outcomes when treatment decision were made using the Oncotype DX Recurrence Score, along with clinical factors such as age, tumor size, grade and treatment, and the Adjuvant! Online risk assessment tool.
In the study, researchers found that the Oncotype DX Recurrence Score had a statistically significant prognostic value beyond the prognosis of the Adjuvant! risk assessment tool in both node-negative (p<0.001) and node-positive (p=0.003) patients. Patients in the ATAC trial who were on anastrozole had greater efficacy and the similar hazard ratios for the recurrence score in both treatment arms. This finding “suggests a lower risk of recurrence in patients treated with aromatase inhibitors,” the researchers said in a statement. In addition, an increase likelihood of distant metastases was noted for any recurrence score when patients presented with greater numbers of positive nodes.
"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," Mitch Dowsett of Royal Marsden Hospital and lead author of the study said in a statement. "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."
This is the largest study Genomic Health has conducted to date for Oncotype DX, according to the company.
Another study presented by Genomic Health at the conference found that quantitative RT-PCR analysis is possible in ductal carcinoma in situ that is adjacent to invasive ductal carcinoma. “Of the 30 ER-positive breast cancer tumor samples that were identified, 90 percent had sufficient RNA for Oncotype DX analysis, after separating the DCIS and IDC tissues,” researchers said in a statement. “While DCIS adjacent to invasive breast cancer demonstrated similar quantitative biology for the genes evaluated in the Oncotype DX assay, future studies to evaluate Oncotype DX and recurrence rates in DCIS are needed.”