Abstract
Background: At the 13th St Gallen International Breast Cancer Conference in 2013, a new definition of luminal A-like and luminal B-like breast cancer was proposed, involving the expression of Estrogen Receptor (ER), Progesterone Receptor (PgR), and Ki-67. We examined the rate of concordance between the risk groups using the Oncotype DX Recurrence Score (RS) and the previous and newly proposed luminal subtypes with the standardized Ki-67 assessment.
Method: The relationship between a previously and newly proposed, immunohistochemically defined luminal A and B subtype with the Oncotype DX RS of 41 cases of T1-2 N0-1 M0 (ER positive, HER2 negative) breast cancer was assessed. We first classified the patients into the previously defined luminal A and B subtypes, according to the level of Ki-67 as either “low” (<14%) or “high” (≥14%), as assessed by local pathologists. Next, to consider the necessity for standardizing Ki-67 measurement methods, we re-examined Ki-67 with a central review. By introducing PgR positivity (≥20%), we classified these patients to newly proposed luminal subtypes and compared them with the risk groups stratified by Oncotype DX RS.
Results: In the previously proposed luminal subtypes, the concordance rate between luminal A and the low RS category was 76.5% according to local pathologists and 90.1% by central review, whereas the rate between luminal B and the intermediate to high RS category was 46.7% and 45.8%, respectively. In newly proposed luminal subtypes, the concordance rate between luminal A and low RS category was 100% and between the luminal B and intermediate to high RS category was 53.6%.
Conclusion: Although this study was based on a retrospective chart review of a small sample size, the newly proposed luminal subtypes, including addition of PgR positivity, appeared to improve the precision of selecting patients with intermediate to high RS categories.
Citation
Mizuno Y, Fuchikami H, Takeda N, Yamada J, Inoue Y and Seto H et al., Comparing Oncotype DX Recurrence Score Categories with Immunohistochemically Defined Luminal Subtypes. SM J Surg. 2015;1(1):1005.