Predicting response to neoadjuvant chemotherapy in nonmetastatic hormone receptor-positive breast cancer using 21-gene Breast Recurrence Score test.

Abstract

e12093 Background: The Recurrence Score (RS) result based on the 21-gene Oncotype DX Breast Recurrence Score assay is standard of care in deciding adjuvant chemo-hormonal therapy versus hormone therapy alone in hormone-receptor positive (HR+), HER 2 negative, node–negative breast cancer. This study explores the role of RS result in predicting the response to neoadjuvant chemotherapy (NACT). Methods: In this retrospective single institution cohort study, electronic medical records of 148 women with HR+, HER 2 negative, non-metastatic breast cancer who received NACT from 2006 onward were screened. 38 patients were excluded due to lack of tissue for testing. Pretreatment biopsy blocks were sent to Genomic Health, Inc. for Oncotype Dx testing. Low RS result was defined as ≤25. Pathologic complete response (pCR) was defined as no residual tumor. Partial response (PR) was residual tumor with > 25% decrease in the largest dimension. No response (NR) was defined as < 25% decrease in the tumor post NACT. Progression (PD) was defined as increase in size of original tumor or new site(s) of disease. Results: Of the 110 patients studied, 58% were postmenopausal women. Fifty percent were African American, 12% were Caucasian and 27% were Hispanic. Invasive ductal carcinoma was the predominant histology (86%). Most patients had > T2 disease (97%) with 73% being clinically node positive. Adriamycin based NACT regimen was used in treating 86.3% of the women. Forty patients (36.4%) had tumor with RS≤25. NR/PD was significantly higher in tumors with RS≤25 (27/40) vs RS > 25 (13/70) (OR: 9.1, 95% CI: 3.7-22.2, P< 0.001). pCR was seen in 16% with RS > 25 and 0% with RS ≤25. Response to NACT (pCR/PR) was 32.5% in RS≤25 vs 81.4% in RS > 25. In tumors with response, RS > 25 was associated with a greater percent decrease in the tumor size compared to RS≤25 (median decrease of 71% vs 52%, P= 0.033). Conclusions: HR+, HER 2 negative, RS≤25 breast cancer is associated with increased rates of NR/PD and is unlikely to respond to NACT. Recurrence Score result determination in pretreatment breast cancer biopsy samples can be an effective tool to select patients with non-metastatic breast cancer for NACT. Studies are needed to determine novel neoadjuvant therapeutic approaches in patients who are candidates for neoadjuvant therapy but are unlikely to benefit from NACT.