Combining TMEM Doorway Score and Mena(Calc) Score Improves the Prediction of Distant Recurrence Risk in HR+/HER2-Breast Cancer Patients

Simple Summary 90% of breast cancer mortality is caused by distant metastasis, a process that involves both dissemination of cancer cells to distant sites as well as their proliferation after arrival. However, prognostic assays currently used in the clinic are based on proliferation and do not measure tumor cell dissemination potential. We previously reported that the density of Tumor Microenvironment of Metastasis (TMEM) doorways (portals for cancer cell intravasation and dissemination) is a prognostic biomarker for the development of distant metastasis in hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) patients. We have shown further that Mena(Calc), a mechanistically linked (but independent) biomarker for distant metastasis, is prognostic in some cohorts of triple-negative patients. Here, we develop and compare several digital pathology-based machine vision algorithms to investigate if a combined TMEM-Mena(Calc) biomarker could provide improved prognostic information over and above that of either biomarker alone. Purpose: to develop several digital pathology-based machine vision algorithms for combining TMEM and Mena(Calc) scores and determine if a combination of these biomarkers improves the ability to predict development of distant metastasis over and above that of either biomarker alone. Methods: This retrospective study included a subset of 130 patients (65 patients with no recurrence and 65 patients with a recurrence at 5 years) from the Calgary Tamoxifen cohort of breast cancer patients. Patients had confirmed invasive breast cancer and received adjuvant tamoxifen therapy. Of the 130 patients, 86 cases were suitable for analysis in this study. Sequential sections of formalin-fixed paraffin-embedded patient samples were stained for TMEM doorways (immunohistochemistry triple staining) and Mena(Calc) (immunofluorescence staining). Stained sections were imaged, aligned, and then scored for TMEM doorways and Mena(Calc). Different ways of combining TMEM doorway and Mena(Calc) scores were evaluated and compared to identify the best performing combined marker by using the restricted mean survival time (RMST) difference method. Results: the best performing combined marker gave an RMST difference of 5.27 years (95% CI: 1.71-8.37), compared to 3.56 years (95% CI: 0.95-6.1) for the associated standalone TMEM doorway analysis and 2.94 years (95% CI: 0.25-5.87) for the associated standalone Mena(Calc) analysis. Conclusions: combining TMEM doorway and Mena(Calc) scores as a new biomarker improves prognostication over that observed with TMEM doorway or Mena(Calc) Score alone in this cohort of 86 patients.