Breast Cancer Staging: Updates in the AJCC Cancer Staging Manual 8th Edition and Current Challenges for Radiologists, From the AJR Special Series on Cancer Staging

The standardization of the breast cancer TNM staging system by the AJCC allows physicians to evaluate patients with breast cancer using standard language and criteria, to assess treatment response, and to compare patient outcomes. Previous editions of the AJCC Cancer Staging Manual relied on the anatomic TNM method of staging that incorporates imaging and employs population-level survival data to predict patient outcomes. Recent advances in therapy based on biomarker status and multigene panels have advanced treatment strategies. In the AJCC Cancer Staging Manual's newest edition (8th edition, adopted on January 1, 2018), breast cancer staging integrates anatomic staging with tumor grade, biomarker data of hormone receptor status, oncogene expression, and gene expression profiling, to assign prognostic stage. This article reviews the AJCC 8th edition breast cancer staging system with a focus on anatomic staging and the challenges that anatomic staging poses for radiologists. We highlight key imaging findings that impact patient management and discuss the role of imaging in evaluating response to neoadjuvant therapy. Finally, we discuss biomarkers and multigene panels and how these impact prognostic stage. The review will help radiologists identify critical findings that affect breast cancer staging as well as understand ongoing limitations of imaging in staging.