The influence of the 21-gene recurrence score assay on decision making about adjuvant chemotherapy in stage I-II estrogen receptor-positive breast cancer: Experience at a single center with a uniform treatment policy.

Abstract

660 Background: The 21-gene assay (OncotypeDx) recurrence score (RS) has been validated in retrospective studies as prognostic of distant disease recurrence and predictive of benefit of chemotherapy in estrogen receptor (ER)-positive breast cancer. Published data on the impact of the assay on clinical practice is limited. We analyze the influence of the RS on decision making in 135 patients seen in a single practice with a unified treatment policy. Methods: Patients with stage I and II breast cancer, ER-positive, Her2-negative who had no contraindications to chemotherapy were eligible. Clinical and pathologic data were recorded, as was the recommendation on adjuvant chemotherapy both before and after obtaining the RS. The test was performed by Genomic Health (Redwood City, CA, USA) on paraffin imbedded tissue from surgical specimens or biopsies. Our treatment policy was to give adjuvant chemotherapy for high risk RS (> 30), endocrine therapy alone for low risk RS (< 18), and for intermediate risk RS (18-30) to decide based on classical clinicopathologic features. Results: From 2/2006 to 6/2009 RS was obtained on 135 patients, including 3 males. Median age 58 (range 33-75). Histologic grade: low 36 (26.7%), intermediate 82 (60.7%), high 7 (5.2%), undetermined 10 (7.4%). Node-negative: 115 (85.2%). RS results: median 19 (range 1-57). RS risk: low 70 (51.9%), intermediate 50 (37%), high 15 (11.1%). Prior to RS result, 64 (47.4%) were recommended for chemotherapy, while after RS result 50 (37.0%) were recommended for chemotherapy. Of the 34 (25.2% [95%CI 17.9-32.5]) patients for whom recommendation was changed, 10 (7.4%) were changed to chemotherapy, and 24 (17.8%) were changed to endocrine therapy. Recommendation was unchanged in 101 (74.8% [95%CI 67.4-82.1%]). RS was independent of T stage, Ki67, and ethnic group. There were insufficient cases of high grade to evaluate correlation with grade. Conclusions: The 21-gene RS, when applied in a consistent manner in early stage breast cancer, changes the treatment plans in one quarter of patients tested. No significant financial relationships to disclose.