Usefulness of Prognostic Stage in High-Risk Early Luminal Breast Cancer
TL;DR
American Joint Committee on Cancer PS offers superior prognostic stratification compared to UICC AS in high-risk luminal breast cancer, and incorporation into clinical practice may enable more personalized treatment approaches, particularly when identifying candidates for adjuvant abemaciclib therapy.
Abstract
Introduction: Breast cancer remains the most prevalent malignancy among women worldwide, with prognostic outcomes and therapeutic responses differing considerably across subtypes. The conventional staging framework developed by the Union for International Cancer Control (UICC), based on the Tumor, Node, Metastasis classification, reflects anatomical stage (AS) but overlooks biological characteristics. To address this limitation, the American Joint Committee on Cancer (AJCC) introduced the Prognostic Stage (PS) in its 8th edition, which integrates biomarkers including estrogen receptor (ER), progesterone receptor (PgR), human epidermal growth factor receptor 2 (HER2), and histological grade (HG). This study aimed to assess and compare the prognostic utility of UICC AS and AJCC PS in patients with high-risk luminal breast cancer. Methods: This retrospective study included patients who underwent surgery for ER-positive, HER2-negative breast cancer at Tokyo Metropolitan Komagome Hospital from 2011 to 2018. High-risk classification was defined based on MonarchE trial criteria: axillary lymph node metastasis, tumor diameter ≥5 cm, HG3, or Ki-67 ≥20%. Staging was performed using both UICC AS and AJCC PS, and prognostic values were evaluated via Kaplan-Meier survival analysis. Results: Among 105 eligible cases, 43 (41%) were downstaged when reclassified from UICC AS to AJCC PS. While UICC AS failed to yield significant stratification in terms of invasive disease-free survival (IDFS) and distant recurrence-free survival (DRFS), AJCC PS demonstrated significant prognostic discrimination (IDFS p = 0.014; DRFS p = 0.004). Conclusions: American Joint Committee on Cancer PS offers superior prognostic stratification compared to UICC AS in high-risk luminal breast cancer. Its incorporation into clinical practice may enable more personalized treatment approaches, particularly when identifying candidates for adjuvant abemaciclib therapy. Further validation through larger, prospective studies is warranted.