Comment to "Patients with Concordant Triple-Negative Phenotype between Primary Breast Cancers and Corresponding Metastases Have Poor Prognosis".

To the Editor,

I read the article by Shin et al. [1] regarding the prognostic impact of discordance between the receptor status of primary breast cancers and corresponding metastases. They concluded that patients with concordant triple-negative phenotype (TNP) had worse long-term outcomes than patients with concordant non-TNP and discordant TNP in a comparison of primary and metastatic breast cancer. As described in the “Methods” section, the cutoff value for estrogen receptor and progesterone receptor positivity was ≥10% of tumor cells positive for nuclear staining. However, in the literature, many studies on TNP describe hormone receptor status with different cutoff values [23]. Furthermore, the American Society of Clinical Oncology and College of American Pathologists (ASCO/CAP) recommended that a cutoff of 1% positive cells be used to define estrogen receptor-positive status [4]. In conclusion, for better interpretation of studies related to TNP, as in the case of the definition of human epidermal growth factor receptor 2 status, internationally accepted defined cutoff values for hormone receptors are urgently needed.

As noted in the commentary, the American Society of Clinical Oncology and College of American Pathologists (ASCO/CAP) guideline recommendations for estrogen receptor (ER) and progesterone receptor (PR) positivity were revised from 10% to 1% in 2010 [1]. Patients with breast cancer in this study underwent primary surgery and biopsy for distant metastasis from 2000 to 2010 and the cutoff value for ER and PR positivity was 10% [2]. Many studies on patients with breast cancer before 2010 defined ER and PR positivity as ≥10% of tumor cells positive for nuclear staining [34]. Furthermore, other studies reported that weakly ER/PR-positive breast cancer that had 1% to 10% positivity showed a survival rate intermediate between those of strongly ER-positive and ER-negative breast cancers [5]. Therefore, I agree that a cutoff value for ER and PR positivity should be 1% after a new guideline is established. However, as our study included patients before 2010, this cutoff value is acceptable for this study.