Differences in Clinical Outcomes between Luminal A and B Type Breast Cancers according to the St. Gallen Consensus 2013

Abstract

Purpose: Human epidermal growth factor receptor 2 (HER2)-positive luminal B type comprises estrogen receptor (ER)-positive and HER2-positive cancers, and HER2-negative luminal B type comprises ER-positive cancers showing a Ki-67 labeling index ≥14% or progesterone receptor (PR) expression of <20% according to the St. Gallen consensus 2013. The current study aimed to classify intrinsic subtypes according to the St. Gallen consensus 2013 and determine the differences in clinicopathological parameters and survival outcomes among the molecular types, especially among the luminal types.

Methods: Assessment of molecular types was performed for 267 invasive ductal carcinomas. The differences in clinicopathological parameters, disease-free survival (DFS), and overall survival (OS) among the molecular types were analyzed.

Results: The luminal B type was the most prevalent, at 44.9%, followed by the luminal A, triple-negative (including basal-like type), and HER2 type, at 21.7%, 18.7%, and 14.6%, respectively. There were statistically significant differences in size (p=0.003), nodal status (p=0.046), histologic grade (p<0.001), p53 (p<0.001) and cyclooxygenase 2 (COX-2) positivity (p=0.002), recurrence (p=0.001) and death rates (p=0.036), DFS (p=0.002), and OS (p=0.039) among the molecular types. Significant differences in size (p=0.009), nodal metastasis (p=0.019), histologic grade (p<0.001), p53 positivity (p=0.001), and PR expression (p<0.001) were noted between the luminal A and B types. Among the luminal B type cancers, the distributions of ER and PR scores showed significant differences (p=0.003, p=0.003). p53 positivity in the luminal B type cancers was related to shortened DFS (p=0.034). In luminal type cancers, COX-2 positivity was related to longer DFS (p=0.026).

Conclusion: Different management guidelines should be considered for the luminal A and luminal B breast cancer types. Positive p53 expression in luminal B type cancers and negative COX-2 expression in luminal type cancers seem to be related to poor clinical outcome.

Keywords: Breast neoplasms; Ki-67 antigen; Molecular type; Progesterone receptors.

Figure 1. Immunohistochemical stains for Ki-67 in the breast cancers. Low labeling index (<10%) (A), intermediate (10%-20%) (B), and high labeling index (>20%) (C) based on Eye-10 method (×100).

Figure 2. Immunohistochemical stains for p53 and cycloxygenase 2 (COX-2) in the breast cancers. More than two-thirds of the tumor cells is regarded as p53 positive (A, ×40), and diffuse (>50%) and/or strong reaction is regarded as COX-2 positive (B, ×100).

Figure 3. Comparison of disease-free survival (DFS) and overall survival (OS) with respect to the molecular types of breast cancers. Statistically significant differences among the molecular types of DFS (A) and OS (B) are seen, but no significant differences of DFS (C) and OS (D) between the luminal A and B types.

Figure 4. Comparison of disease-free survivals (DFS) and overall survivals (OS) according to p53 expression in the luminal type cancers, and in the luminal B type cancers. Shortened DFS is noted in p53 positive luminal type cancers (p=0.084) (A), and in p53 positive luminal B type cancers (p=0.034) (C), but there were no significant differences of OS in the luminal type cancers (B) and the luminal type B cancers (D).