Clinical significance of 21-gene recurrence score assay for hormone receptor-positive, lymph node-negative breast cancer in early stage

Abstract

Objective: To identify the relationship between clinical pathological characteristics and the recurrence score (RS) on a 21-gene expression assay in patients with hormone receptor-positive, node-negative breast cancer, as well as the effect of RS on adjuvant decision-making.

Methods: The retrospective study was conducted among luminal breast cancer patients admitted to Xijing Hospital between October 10, 2016, and September 14, 2018. Real-time PCR was used for 21-genome detection. Based on the calculated RS, participants were classified into low-risk, moderate-risk, and high-risk groups. Single-factor analysis and multiple logistic regression analysis were performed to explore independent predictors of high RS. Moreover, the effect of RS on adjuvant decision-making was studied.

Results: Two hundred twenty-two patients with luminal breast cancer, aged 48.3 ± 9.66, were enrolled. Among them, 33.8% had low (13 ± 3.34), 45.5% intermediate (23 ± 3.65), and 20.7% high (37 ± 3.44) RS. According to the single-factor analysis, age, tumor size, Ki-67, molecular subtype, CK5/6 expression, E-cadherin level, and histological grade were positively associated with high RS. Multiple logistic analyses showed that tumor size and histological grade were independent variables that might predict high RS in patients with hormone receptor-positive, node-negative breast cancer. For adjuvant decision-making, the proportion of adjuvant chemotherapy in the intermediate-/high-risk groups was higher than that in the low-risk group, P < 0.001. Compared with the data worldwide, the changes of treatment selection in the present study were similar to those in Japan (23.0% vs. 26%) and America (23.0% vs. 23.0%). Considering the pathology types, 14.3% of patients with invasive breast cancer with lower RS changed treatment recommendations, predominantly from chemo-endocrine to endocrine treatment alone, whereas the percentage in intermediate/high RS groups was 8.1%.

Conclusions: Tumor size and histological grade were independent variables, predicting high risk in patients with hormone receptor-positive, node-negative breast cancer; 21-gene RS assessment was potentially a critical tool in guiding adjuvant decision-making in China.

Keywords: 21-Gene oncotype Dx; Adjuvant decision-making; Breast cancer; Independent predictors; Recurrence risk.