Assessing the long-term prognostic ability of the 70 gene expression signature MammaPrint in an Italian single-center prospective cohort study of early-stage intermediate-risk breast cancer patients

Purpose: The aim of this study was to assess the prognostic performance of the 70-gene signature, MammaPrint, in an Italian single-center prospective cohort of early-stage intermediate-risk breast cancer (BC) patients. Methods: A total of 195 eligible early BC cases were tested for genomic risk between 2006 and 2013. In this retrospective analysis, the association of genomic risk with distant metastasis-free survival (DMFS) and overall survival (OS) were assessed using Cox regression models, adjusting for clinical and pathological tumor characteristics. Results: MammaPrint identified 118 (60.5 %) patients with genomically Low Risk tumors and 77 (39.5 %) patients with genomically High Risk tumors. Age, menopausal status, tumor size, receptor status, and nodal status were comparable between MammaPrint Risk categories. The median follow-up was 8.4 years for DMFS and 9.3 years for OS; 8-year follow-up was reported for both endpoints. The 8-year DMFS was 90.4 % (95 % CI 84.9–95.9) in patients with MammaPrint Low Risk tumors compared to 60.8 % (95 % CI 49.8–71.8) for patients with High Risk tumors. Patients with MammaPrint Low Risk tumors exhibited significantly superior 8-year OS (97.3 %; 95 % CI 94.4–100) compared with MammaPrint High Risk tumors (89.5 %; 95 % CI 82.6–96.4; p = 0.028). Multivariate analyses identified MammaPrint as significantly associated with 8-year DMFS and MammaPrint together with Progesterone Receptor positivity with 8-year OS. Conclusion: The prognostic performance of MammaPrint was demonstrated in early-stage clinically intermediate to high-risk BC patients. Moreover, patients with MammaPrint Low Risk tumors had good outcome regardless of treatment regimen, thus supporting personalized treatment choices.