Researchers affiliated with the TransATAC Study have reported that the Oncotype DX® test predicts the risk of distant cancer recurrence in postmenopausal women with early, hormone receptor-positive breast cancer with both node-negative and node-positive disease treated with tamoxifen (Nolvadex®) or anastrozole (Arimidex®). These results were published early online in the Journal of Clinical Oncology on March 8, 2010.

Oncotype DX is a genomic test that has been shown to predict the likelihood of distant cancer recurrence and the likelihood of chemotherapy benefit in women with early-stage, estrogen receptor-positive breast cancer treated with tamoxifen. The test evaluates the activity of 21 genes from a sample of the patient’s cancer to determine the patient’s Recurrence Score. The higher the Recurrence Score, the higher the risk of cancer recurrence. Oncotype DX has been added to U.S. medical guidelines for early-stage breast cancer.

The current analysis assessed how the Recurrence Score performed among women treated with the aromatase inhibitor drug anastrozole and among those with node-positive breast cancer.

The researchers collected information from 1,231 women who participated in the ATAC (Anastrozole, Tamoxifen, Alone or in Combination) study. The study enrolled postmenopausal women with early, hormone receptor-positive breast cancer. Study participants received hormonal therapy with either tamoxifen or anastrozole.

The Recurrence Score predicted the risk of distant cancer recurrence among women with node-negative and node-positive breast cancer:

• Among women with node-negative breast cancer, the nine-year risk of distant cancer recurrence was 4% among women with a low Recurrence Score, 12% among women with an intermediate Recurrence Score, and 25% among women with a high Recurrence Score.
• Among women with node-positive breast cancer, nine-year risk of distant cancer recurrence was 17% among women with a low Recurrence Score, 28% among women with an intermediate Recurrence Score, and 49% among women with a high Recurrence Score.
• The relationship between Recurrence Score and risk of distant cancer recurrence was similar regardless of the type of hormonal therapy that the women received.

Comments: This study suggests that the Oncotype DX test provides information about risk of distant cancer recurrence in both node-negative and node-positive, hormone-receptor positive breast cancer. Furthermore, Oncotype DX was predictive of distant recurrence risk among women treated with tamoxifen as well as women treated with anastrozole.

Reference: Dowsett M, Cuzick J, Wales C et al. Prediction of risk of distant recurrence using the 21-gene recurrence score in node-negative and node-positive postmenopausal patients with breast cancer treated with anastrozole or tamoxifen: a TransATAC study. Journal of Clinical Oncology [early online publication]. March 8, 2010.