The impact of Oncotype DX® recurrence score of paraffin-embedded core biopsy tissues in predicting response to neoadjuvant chemotherapy in women with breast cancer

Abstract

Background: Oncotype DX® test is beneficial in predicting recurrence free survival in estrogen receptor positive (ER+) breast cancer. Ability of the assay to predict response to neoadjuvant chemotherapy (NCT) is less well-studied.

Objective: We hypothesize a positive association between the Oncotype DX® recurrence score (RS) and the percentage tumor response (%TR) after NCT.

Methods: Pre-therapy RS was measured on core biopsies from 60 patients with ER+, HER2- invasive breast cancer (IBC) who then received NCT. Pre-therapy tumor size was measured using imaging. %TR, partial response (PR; >50%), pathologic complete response (pCR) and breast conserving surgery (BCS) rates were measured.

Results: Median RS was 20 (2-69). Median %TR was 42 (0-97)%. PR was observed in 43% of patients. There was no association between %TR and pre-NCT tumor size, age, Nottingham score or nodal status (p > 0.05). No statistically significant association with %TR was seen with RS as a categorical or continuous variable (p = 0.21 and 0.7, respectively). Response to NCT improved as ER (p = 0.02) by RT-PCR decreased. Lower ER expression by IHC correlated with response (p = 0.03).

Conclusions: In patients with ER+ IBC receiving NCT, RS did not predict response to NCT using %TR. The benefit of the assay prior to NCT requires further study.

Keywords: 21 gene assay; Estrogen positive; breast cancer; neoadjuvant; response; tumor volume reduction.