A retrospective study based on patients treated in a randomized clinical trial showed that the 21-gene recurrence score (RS) predicts favorable vs. unfavorable outcomes after chemotherapy for patients with estrogen receptor (ER)-positive breast cancer that has spread to axillary lymph nodes. 

Researchers presented the results at the 2012 Breast Cancer Symposium.  The Symposium is co-sponsored by the American Society of Breast Disease, the American Society of Breast Surgeons, the American Society of Clinical Oncology, the American Society for Radiation Oncology, the National Consortium of Breast Centers and the Society of Surgical Oncology.

The results of this study refine risk of recurrence and death in node-positive, ER-positive patients who are treated with adjuvant chemotherapy plus hormonal (endocrine) therapy and may help tailor the extent of adjuvant chemotherapy in these patients. More accurate estimation of risk of recurrence and death in node-positive patients after adjuvant chemotherapy could assist in selection of appropriate candidates for clinical trial evaluating novel adjuvant therapies.

RS has previously been reported to be prognostic of distant recurrence and survival outcomes for patients with node-negative and node-positive disease treated with adjuvant hormonal therapy. RS was also found to be prognostic in patients with up to three positive nodes treated with adjuvant endocrine therapy plus adjuvant chemotherapy. This study, for the first time, demonstrates that RS is a significant predictor of favorable and unfavorable outcomes after adjuvant hormonal therapy plus chemotherapy in ER-positive breast cancer patients with any number of positive nodes.

"The number of positive nodes is a strong prognostic factor in breast cancer patients. The risk increases with more positive nodes. However, even within the nodal categories, the RS further subdivides patients into distinct risk levels. So, it is an additional prognostic factor because it accounts for the biology of the disease," said lead author Eleftherios P. Mamounas, MD, Medical Director of the Cancer Center at Aultman Hospital in Canton, Ohio.

The study explored the prognostic impact of the recurrence score (RS) in 1,065 node-positive, estrogen receptor (ER)-positive breast cancer patients who had received anthracycline- or anthracycline/taxane based chemotherapy plus hormonal therapy as part of a randomized clinical trial. The researchers calculated recurrence scores using tissue specimens from past breast surgeries and then correlated the RS with disease-free and overall survival.

The analysis showed that the 10-year disease-free survival, absence of distant recurrence, and overall survival were 76 percent, 81 percent, and 90 percent, respectively, among women with low RS, and 48 percent, 56 percent, and 63 percent, respectively, among those with high RS. Furthermore, RS provided prognostic information in addition to clinical factors such as age, tumor size, grade and number of positive lymph nodes.

RS is calculated based on a commercially available test that looks at the expression of cancer-related genes in breast tumor tissue obtained at surgery. The test is commonly used in clinical practice to estimate risk of recurrence as well as likelihood of benefiting from chemotherapy.