Breast cancer tumor heterogeneity has only little impact on the estimation of the Oncotype DX® recurrence score using Magee Equations and Magee Decision Algorithm™

Prognostic Implications of Magee Equation 3 and Residual Cancer Burden in Patients Receiving Neoadjuvant Chemotherapy for Hormone Receptor-Positive HER2-Negative Breast Cancer

Breast cancer (BC) presents significant molecular heterogeneity, complicating prognosis and treatment strategies. Although molecular testing enhances our understanding of BC, high costs can limit accessibility in certain health care settings. This retrospective cohort study evaluates the prognostic value of Magee equation 3 (ME3) and residual cancer burden (RCB) in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative BC treated at the Instituto do Câncer do Estado de São Paulo from January 2011 to January 2024. We included 203 women, with a mean age of 50.2 years, diagnosed with hormone receptor-positive, human epidermal growth factor receptor 2-negative BC (stages I-III), who completed neoadjuvant chemotherapy followed by surgery. ME3 scores were categorized as low (<18), intermediate (18-25), and high (>25), whereas RCB was classified into 4 groups (0, 1, 2, or 3). Associations between ME3 and RCB categories were analyzed using χ2 and Cochran-Mantel-Haenszel tests. Overall survival (OS) and disease-free survival (DFS) were assessed using the Kaplan-Meier method with log-rank tests. Prior to neoadjuvant chemotherapy, 60.1% of patients had tumors >5 cm, 69.5% had positive lymph nodes, and 85.7% had invasive carcinoma of nonspecial type, with a mean Ki67 index of 35.5%. Analysis revealed that 22.2% of patients had ME3 >25, 39.9% had ME3 18-25, and 37.9% had ME3 <18. A significant inverse association was found between RCB and ME3 (P < .0001). At a median follow-up of 91.4 months (range: 8-157 months), significant associations were noted for OS (log-rank P = .0059) and DFS (log-rank P = .0028) with ME3 categories; patients with low ME3 showed better outcomes. In patients with RCB-3, those with ME3 <18 had a lower risk of recurrence compared with those with ME3 18-25 (hazard ratio: 4.70, 95% CI: 2.00-11.02; P = .0004) and ME3 > 25 (hazard ratio: 5.18, 95% CI: 1.85-14.15; P = .0017). Similarly, lower risks of death were observed for ME3 < 18 versus higher ME3 categories. In conclusion, ME3 significantly correlates with OS and DFS, suggesting that it may serve as a valuable alternative to molecular assays in resource-limited settings. Combining ME3 with RCB enhances individualized risk stratification, providing a more precise prognostic assessment for patients with high RCB.

The Story of the Magee Equations: The Ultimate in Applied Immunohistochemistry

Magee equations (MEs) are a set of multivariable models that were developed to estimate the actual Onco type DX (ODX) recurrence score in invasive breast cancer. The equations were derived from standard histopathologic factors and semiquantitative immunohistochemical scores of routinely used biomarkers. The 3 equations use slightly different parameters but provide similar results. ME1 uses Nottingham score, tumor size, and semiquantitative results for estrogen receptor (ER), progesterone receptor, HER2, and Ki-67. ME2 is similar to ME1 but does not require Ki-67. ME3 includes only semiquantitative immunohistochemical expression levels for ER, progesterone receptor, HER2, and Ki-67. Several studies have validated the clinical usefulness of MEs in routine clinical practice. The new cut-off for ODX recurrence score, as reported in the Trial Assigning IndividuaLized Options for Treatment trial, necessitated the development of Magee Decision Algorithm (MDA). MEs, along with mitotic activity score can now be used algorithmically to safely forgo ODX testing. MDA can be used to triage cases for molecular testing and has the potential to save an estimated $300,000 per 100 clinical requests. Another potential use of MEs is in the neoadjuvant setting to appropriately select patients for chemotherapy. Both single and multi-institutional studies have shown that the rate of pathologic complete response (pCR) to neoadjuvant chemotherapy in ER+/HER2-negative patients can be predicted by ME3 scores. The estimated pCR rates are 0%, <5%, 14%, and 35 to 40% for ME3 score <18, 18 to 25, >25 to <31, and 31 or higher, respectively. This information is similar to or better than currently available molecular tests. MEs and MDA provide valuable information in a time-efficient manner and are available free of cost for anyone to use. The latter is certainly important for institutions in resource-poor settings but is also valuable for large institutions and integrated health systems.