Breast Cancer Index – pro
Breast Cancer Index is a validated tool to help with patient selection for extended endocrine therapy in ER+ early stage breast cancer. The BCI is an assay comprised of 2 independently developed biomarkers that predicts 10-year distant recurrence rates over and above the Clinical Tumor Score (CTS), which is a composite of involved nodes, tumor grade and size, age, and treatment. In a multivariate analysis that controlled for risk factors, the Breast Cancer Index (BCI), but neither the Oncotype Dx Recurrence Score (RS; Genomic Health) nor a standard IHC4 assay, was significantly prognostic of distant recurrence 5 to 10 years after a disease-free period. However, there are no studies that show its utility in improving statistics for patients when used prospectively.
While there continues to be a debate regarding this point, a recent study by Bartlett et al, Trans-aTTom is a multi-institutional, prospective-retrospective study in patients with available formalin-fixed paraffin-embedded primary tumor blocks. BCI testing and central determination of estrogen receptor (ER) and progesterone receptor (PR) status by immunohistochemistry were carried out blinded to clinical outcome. Survival endpoints were evaluated using Kaplan-Meier analysis and Cox regression with recurrence-free interval (RFI) as the primary endpoint. Interaction between extended endocrine therapy and BCI (H/I) was assessed using the likelihood ratio test. CI by high H/I expression was predictive of endocrine response and identified a subset of HR+, N+ patients with significant benefit from 10 versus 5years of tamoxifen therapy. These data provide further validation, consistent with previous MA.17 data, establishing level 1B evidence for BCI as a predictive biomarker of benefit from extended endocrine therapy.
e National Comprehensive Cancer Network (NCCN) and the American Society of
Clinical Oncology (ASCO) recognize BCI as the only gene expression assay to predict
the benefit of extended endocrine therapy when considering adjuvant systemic therapy.
The NCCN & ASCO recommendation includes both node-positive and negative patients
across anti-estrogen therapies, including tamoxifen and aromatase inhibitors. No other
genomic test has been shown to be predictive of the likelihood of benefit from extended
endocrine therapy, and analyses of the extended endocrine therapy trials have
consistently demonstrated that traditional clinical and pathologic factors (e.g., nodal
status, tumor size, tumor grade, qER, etc.) are NOT predictive of benefit from endocrine
therapy.
• The ASCO guidelines state that If a patient has node-negative or node-positive breast
cancer with 1-3 positive nodes and has been treated with five years of primary endocrine
therapy without evidence of recurrence, the clinician may offer the BCI test to guide
decisions about extended endocrine therapy with either tamoxifen, an AI, or a sequence
One Judiciary Square – 441 4th Street, NW, Suite 250N, Washington, D.C., 20001
of tamoxifen followed by AI (Type: evidence-based; Evidence quality: intermediate;
BCI was prognostic in patients with either node-negative or node-positive disease in the SOFT study.
. O’Regan R, Zhang Y, Fleming GF, et al: Evaluation of the Breast Cancer Index in premenopausal women with early-stage HR+ breast cancer in the SOFT trial. 2022 San Antonio Breast Cancer Symposium. Abstract GS1-06. Presented December 6, 2022.
2. Francis PA, Fleming GF, Lang I, et al: Adjuvant endocrine therapy in premenopausal breast cancer: 12-year results from SOFT. J Clin Oncol. December 9, 2022 (early release online).
NCCN, Breast cancer 2023
Bartlett JMS, Sgroi DC, Treuner K, et al. Breast Cancer Index and prediction of benefit from extended endocrine therapy in breast cancer patients treated in the Adjuvant Tamoxifen-To Offer More? (aTTom) trial. Ann Oncol. 2019;30(11):17761783.