Identification of Early-Stage Breast Cancer with Minimal Risk of Recurrence by Breast Cancer Index.

Abstract

Purpose: This study assessed the prognostic ability of Breast Cancer Index (BCI) to identify patients at minimal risk (<5%) of 10-year distant recurrence (DR) who are unlikely to benefit from adjuvant endocrine therapy.

Experimental design: This prospective translational study included postmenopausal patients with early-stage, HR+ N0 breast cancer from the Stockholm (STO-3) trial who underwent surgery alone ("untreated") or surgery plus adjuvant tamoxifen ("treated") and the Netherlands Cancer Registry (NCR; surgery alone). The primary endpoint was time to DR. An adjusted BCI model with an additional cut-point was developed that stratified patients into 4 prognostic risk groups.

Results: Across cohorts, 16%-22% of patients were classified as minimal risk of 10-year DR. In the Stockholm untreated cohort (n = 283), risks in the minimal, low, intermediate, and high risk groups were 2.3%, 15.5% (hazard ratio, 4.71 [95% CI, 1.09-20.29] versus minimal risk), 19.8% (6.97 [1.61-30.18]), and 35.9% (13.21 [3.07-56.76]), respectively (P < .001). In the Stockholm treated cohort (n = 317), risks were 4.3%, 5.0% (1.16 [0.35-3.85]), 11.7% (2.45 [0.74-8.14]), and 21.1% (5.27 [1.72-16.16]; P < .001). In the NCR cohort (n = 1245), risks were 4.5%, 7.5% (sub-distribution hazard ratio, 1.67 [95% CI, 0.81-3.45]), 10.3% (2.40 [1.14-5.03]), and 13.1% (3.13 [1.50-6.55]; P = .005). BCI risk scores provided additional independent information over standard prognostic factors (likelihood ratio, c2 = 7.98; P = .004).

Conclusions: The adjusted BCI model identified women with early-stage, HR+ N0 breast cancer at minimal risk of DR who may consider de-escalating adjuvant endocrine therapy.