Incorporating Biologic Factors into the American Joint Committee on Cancer Breast Cancer Staging System: Review of the Supporting Evidence

The American Joint Committee on Cancer staging system has evolved in response to improved imaging, refined surgical techniques, enhanced pathologic evaluation, and greater understanding of tumor biology. The 8th edition has introduced clinical and pathologic prognostic stages for breast cancer that incorporate biologic variables (grade, estrogen/progesterone receptor status, HER2 status, multigene panels) with TNM categories that define the anatomic stage. The prognostic staging system facilitates more refined stratification than the anatomic stage with respect to survival and is an important advance that maintains the clinical relevance of the staging system by taking into account tumor biology and current treatment algorithms.