Abstract
Patients with early-stage, hormone receptor–positive breast cancer with favorable clinicopathologic features are often not recommended for extended endocrine therapy. However, even patients with T1N0 disease remain at significant risk of distant recurrence up to 15 years following 5 years of endocrine therapy, highlighting the need for further stratification based on individualized risk to select patients for extended endocrine therapy. In this study, the incremental utility of genomic classification to stratify clinically low-risk patients for late distant recurrence was evaluated using the Breast Cancer Index. In 547 T1N0 patients from two cohorts that were disease-free at 5 years post-diagnosis, Breast Cancer Index categorized 32 and 36% from each cohort, respectively, with high risk of late distant recurrence that was associated with significantly reduced distant recurrence-free survival (86.7 and 89.6%) between years 5–15 and 5–10 compared to Breast Cancer Index low risk (95.4%; P = 0.0263 and 98.4%; P = 0.008). Findings support consideration of genomic classification in clinically low-risk hormone receptor–positive patients to identify candidates for extended endocrine therapy.
Highlights
A number of clinical trials have demonstrated that continuing adjuvant endocrine treatment beyond 5 years (extended endocrine therapy (EET)) in this population results in a statistically significant reduction in disease recurrence; the absolute benefit is modest (3–5%) and prolonged endocrine therapy is associated with adverse effects and risk of several serious toxicities
A recent EBCTCG metaanalysis of 46,138 patients investigated the risk of late distant recurrence (DR) in patients treated with 5 years of endocrine therapy based on clinicopathologic risk factors.[4]
The prognostic component of Breast Cancer Index (BCI) is based on a gene-expression signature that was developed through the algorithmic combination of an endocrine response biomarker (HOXB13:IL17BR (H/I)) and a proliferation biomarker (Molecular Grade Index (MGI))[5, 6] and has been validated in multiple randomized trial cohorts to significantly stratify patients for late DR.[6, 7]
Summary
Risk stratification with Breast Cancer Index for late distant recurrence in patients with clinically low-risk (T1N0) estrogen receptor-positive breast cancer. Patients with early-stage, hormone receptor–positive breast cancer (HRBC) are at long-term risk for recurrence following 5 years of endocrine therapy.[1, 2] A number of clinical trials have demonstrated that continuing adjuvant endocrine treatment beyond 5 years (extended endocrine therapy (EET)) in this population results in a statistically significant reduction in disease recurrence; the absolute benefit is modest (3–5%) and prolonged endocrine therapy is associated with adverse effects and risk of several serious toxicities. EET is often not recommended for patients with favorable clinical and pathologic prognostic features (e.g., node negative (N0), ≤2 cm (T1); lower grade).[3] A recent EBCTCG metaanalysis of 46,138 patients investigated the risk of late distant recurrence (DR) in patients treated with 5 years of endocrine therapy based on clinicopathologic risk factors.[4] In this study, patients with T1N0 disease had 4, 9, and 14% risk of DR at years 5–10, 5–15, and 5–20, respectively. Detailed assay methods and cohort characteristics were previously described.[6]
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