Oncotype DX Score Predicts Residual Disease after Chemotherapy

Audrey Andrews

November 2012, Vol 3, No 8 - Breast Cancer Symposium

?San Francisco, CA—The Oncotype DX Recurrence Score (the 21-gene) test can help identify patients with estrogen receptor (ER)-positive breast cancer with any number of positive lymph nodes who will have residual disease after adjuvant chemotherapy, and who may benefit from additional treatment, reported Eleftherios P. Mamounas, MD, Medical Director, Aultman Hospital Cancer Center, Canton, OH, at the 2012 Breast Cancer Symposium.

This new retrospective analysis was conducted by investigators from the National Surgical Adjuvant Breast and Bowel Project (NSABP).

The Oncotype DX Recurrence Score has proved to have expanded utility in guiding treatment decisions. “We can identify patients with high residual risk in spite of receiving chemotherapy. We can try to find a better treatment for them or enroll them in a clinical trial. By contrast, patients with low residual risk may do well with less treatment,” said Dr Mamounas.

Such patients may be sufficiently treated with only 4 cycles of chemotherapy rather than a full course of 8 cycles, including a taxane, Dr Mamounas suggested.

The current analysis indicates that the extent of chemotherapy may be tailored according to the estimation of residual risk, he said.

The Oncotype DX Recurrence Score is currently approved for use in patients with ER-positive, node-negative breast cancer to estimate whether the addition of chemotherapy to endo­crine therapy would be beneficial. This new study shows that the Oncotype DX Recurrence Score can also be applied to patients with ER-positive, node-positive breast cancer who are treated with chemotherapy and with endocrine therapy. In this population, the Recurrence Score was prognostic across the spectrum of subgroups.

The current analysis included 1065 patients who had been treated with adjuvant endocrine therapy and an anthracycline and cyclophosphamide combination, with or without paclitaxel, in the randomized NSABP B-28 clinical trial. Recurrence scores were calculated using tissue specimens from past breast surgeries and then correlating them with outcomes. The median follow-up was 11.2 years.

Robust Independent Predictor of Outcomes
The Recurrence Score was low (<18) in 36% of patients, intermediate (18-30) in 34% of patients, and high (≥31) in 30% of patients.

In a univariate analysis, the Re­currence Score was a significant predictor of disease-free survival (DFS), distant recurrence–free interval, breast cancer–specific survival, and overall survival (OS). In a multivariate analysis, the Recurrence Score provided independent prognostic information for DFS, distant recurrence–free interval, and OS beyond clinical and pathologic factors, including treatment, age, tumor size/grade, number of positive nodes, and type of surgery (P <.001).

Low scores on the test were associated with improved outcomes:

  • DFS was close to 76% among pa­tients with a low score but dropped to 48% for those with a high score
  • OS was 90% for patients with a low score versus 63% for those with a high score.

The Recurrence Score was strongly related to the 10-year risk of recurrence, with events occurring in 54% of patients in the group with high Re­currence Scores versus in 17% of patients with low Recurrence Scores.

Breast cancer–specific deaths oc­curred in 33% of patients with high Recurrence Scores and in 2% of those with low Recurrence Scores.

By treatment assignment, outcomes were very similar between the treatment arms in patients with low Recur­rence Scores, with the benefit of paclitaxel seen mainly in the groups with intermediate and high Recurrence Scores.

Andrew Seidman, MD, a medical on­­cologist at Memorial Sloan-Kettering Cancer Center, New York, commented that the study “highlights the fact that despite hormone receptor positivity and HER2 negativity, many patients will have a high risk of recurrence despite receiving chemotherapy and appropriate endocrine therapy. This gene assay represents a biological tool that may be useful in the future in stratifying patients for clinical trials and in identifying candidates whose outcomes can be improved.”