AUTHOR=Wang Jun , He Zhen-Yu , Dong Yong , Sun Jia-Yuan , Zhang Wen-Wen , Wu San-Gang 

TITLE=The Distribution and Outcomes of the 21-Gene Recurrence Score in T1-T2N0 Estrogen Receptor-Positive Breast Cancer With Different Histologic Subtypes

JOURNAL=Frontiers in Genetics

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2018.00638

DOI=10.3389/fgene.2018.00638

ISSN=1664-8021

ABSTRACT=<p><bold>Background:</bold> The clinical value of 21-gene recurrence score (RS) in various breast cancer histologic subtypes is not well established.</p><p><bold>Aims:</bold> To assess the distribution and outcomes of the 21-gene RS among various T1-T2N0 estrogen receptor-positive breast cancer histologic subtypes.</p><p><bold>Methods:</bold> Using the Surveillance, Epidemiology and End Results database, we investigated the distribution and outcomes of the 21-gene RS among various breast cancer histologic subtypes between 2004 and 2015. The histologic subtypes with 200 or more cases were further analyzed.</p><p><bold>Results:</bold> We identified 83,665 patients including eight histologic subtypes. The most common subtype was invasive ductal carcinoma not otherwise specified (IDC NOS) (77.9%), followed by lobular carcinoma NOS, mixed infiltrating duct and lobular carcinoma (IDC-L), mucinous adenocarcinoma, tubular adenocarcinoma, micropapillary ductal carcinoma, cribriform carcinoma NOS, and intraductal papillary adenocarcinoma with invasion with 10.8, 7.7, 2.1, 0.6, 0.3, 0.2, and 0.2%, respectively. The 5-years breast cancer specific survival (BCSS) was 98.8, 98.8, 98.9, 99.6, 100, 100, 100, and 100%, respectively (<italic>P</italic> = 0.011). Patients with IDC NOS (8.9%), micropapillary ductal carcinoma (8.8%), and intraductal papillary adenocarcinoma with invasion (8.2%) had significantly higher percentage of high-risk RS compared to other histologic subtypes (1.0–3.8%) (<italic>P</italic> &lt; 0.001). The mean RS was higher in IDC NOS, lobular carcinoma NOS, and IDC-L compared to other subtypes. In multivariate analysis, 21-gene RS was the independent prognostic factor in patients with IDC NOS (<italic>P</italic> &lt; 0.001), lobular carcinoma NOS (<italic>P</italic> &lt; 0.001), and IDC-L (<italic>P</italic> &lt; 0.001), patients with a higher RS was associated with poor BCSS.</p><p><bold>Conclusion:</bold> Our results demonstrate that there is a significant difference in distribution of 21-gene RS in T1-T2N0 estrogen receptor-positive breast cancer with different histologic subtypes. Long-term studies with larger series are needed to confirm the role of the 21-gene RS array in prognosis assessment and chemotherapy decision-making in special histologic subtypes with favorable prognosis.</p>