Abstract
Tumor biologic risk has replaced anatomic disease burden for guiding chemotherapy use in HR-positive, early-stage breast cancer. Recent surgical trials support less frequent axillary lymph node dissection, potentially impacting incidence of N2-3 diagnoses. As the field considers applying genomic risk assessment tools for locally advanced, operable HR-positive breast cancer, we estimated current incidence of these cancers, focusing on HR-positive/HER2-negative disease. Of 486,031 cases recorded with Stage I-III HR-positive/HER2-negative disease in the U.S. National Cancer Institute Surveillance, Epidemiology, and End Results-17 database (2010-2021), 28,585 (5.9%) and 23,307 (4.8%) had N2-3M0(Any T) and T3-4N0-1M0 disease, respectively. Invasive lobular cancer, observed across all disease stages and receptor-based subtypes, was highest in HR-positive/HER2-negative locally advanced disease. Incidence of N2-3M0(Any T) decreased for each subtype. Incidence of T3-4N0-1M0 increased for HR-positive/HER2-negative disease but not for the other subtypes. Defining chemotherapy benefit for patients with locally advanced, operable HR-positive breast cancer remains an important clinical question.