Adjusted Breast Cancer Index model identifies minimal-risk groups in premenopausal HR+ node-negative breast cancer

BACKGROUND: An adjusted Breast Cancer Index (BCI) model with an additional cutpoint identified postmenopausal women with hormone-receptor-positive node-negative disease at minimal (<5%) risk of distant recurrence (DR) within 10 years. METHODS: 2025 premenopausal patients with hormone-receptor-positive node-negative breast cancer, randomized to adjuvant endocrine therapy in SOFT and TEXT (35.6% and 40.4% received adjuvant chemotherapy, respectively), previously had BCI assessed. The additional BCI cutpoint re-classified a subset of the low-risk group into minimal-risk; those in intermediate- or high-risk groups were unchanged. The 10-year DR was estimated by Kaplan-Meier method. RESULTS: The adjusted BCI model re-classified 17.8 % and 19.6 % of node-negative disease in SOFT and TEXT into BCI minimal-risk groups; 43.2 % and 38.3 % remained classified in low-risk groups, respectively. In SOFT, the estimated 10-year DR was 2.3 % (95 %CI 0.9-6.0 %) and 4.1 % (95 %CI 2.6-6.5 %) in the minimal-risk and revised low-risk groups, respectively. In TEXT, the estimated 10-year DR was 2.0 % (95 %CI 0.7-6.2 %) and 4.6 % (95 %CI 2.8-7.7 %) in the minimal- and low-risk groups, respectively. CONCLUSIONS: This study confirmed prognostic ability of the minimal-risk BCI cutpoint to classify patients estimated to have minimal-risk of distant recurrence within 10 years among premenopausal patients treated for hormone-receptor-positive node-negative breast cancer, providing relevant information for personalizing adjuvant endocrine therapy. SOFT: (clinicaltrials.gov NCT00066690) TEXT: (clinicaltrials.gov NCT00066703).