The Prognostic Impact of Age at Diagnosis Upon Breast Cancer of Different Immunohistochemical Subtypes: A Surveillance, Epidemiology, and End Results (SEER) Population-Based Analysis

Shibin Cai; Wenjia Zuo; Xunxi Lu; Zongchao Gou; Yi Zhou; Pengpeng Liu; Yin Pan; Shuzheng Chen

doi:10.3389/fonc.2020.01729

The Prognostic Impact of Age at Diagnosis Upon Breast Cancer of Different Immunohistochemical Subtypes: A Surveillance, Epidemiology, and End Results (SEER) Population-Based Analysis

Front Oncol. 2020 Sep 23:10:1729. doi: 10.3389/fonc.2020.01729. eCollection 2020.

Authors

Shibin Cai¹, Wenjia Zuo^{2

3}, Xunxi Lu^{2

3}, Zongchao Gou^{2

3}, Yi Zhou¹, Pengpeng Liu¹, Yin Pan¹, Shuzheng Chen¹

Affiliations

¹ Department of Breast Surgery, Lishui Hospital, Zhejiang University School of Medicine, Lishui, China.
² Department of Breast Surgery, Fudan University Shanghai Cancer Center, Shanghai, China.
³ Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.

Abstract

Background and Objectives: The influence of age at diagnosis of breast cancer upon the prognosis of patients with different immunohistochemical (IHC)-defined subtypes is still incompletely defined. Our study aimed at examining the association of age at diagnosis and risk of breast cancer-specific mortality (BCSM). Methods: 172,179 eligible breast cancer patients were obtained for our study cohort using the Surveillance, Epidemiology, and End Results database from 2010 to 2015. Patients were classified into four IHC-defined subtypes according to their ER, PgR, and HER2 status. Kaplan-Meier plots were used to describe BCSM among patients in different age groups. A Cox proportional hazards model was used for multivariate analysis. A multivariable fractional polynomial model within the Cox proportional hazards model was used to evaluate the relationship between age at diagnosis and the risk of BCSM. Results: For the whole cohort, the median follow-up time was 43 months. Patients younger than 40 years and those older than 79 years presented with the worst BCSM (hazard ratio [HR] 1.13, 95% confidence interval [CI] 1.03-1.23, and HR 3.52, 95% CI 3.23-3.83, respectively, p < 0.01, with age 40-49 years as the reference). The log hazard ratios of hormone receptor (HoR)(+)/HER2(-) patients formed a quadratic relationship between age at diagnosis and BCSM, but not in the other three subtypes of breast cancer. In the HoR(+)/HER2(-) subtype, patients younger than 40 years had worse BCSM than those aged at 40-49 years (HR 1.26, 95% CI 1.10-1.45, and p < 0.01). Conclusions: Women diagnosed with HoR(+)/HER2(-) breast cancer younger than 40 years or older than 79 years of age suffer higher rates of cancer-specific mortality. Young age at diagnosis may be particularly prognostic in HoR(+)/HER2(-) breast cancer.

Keywords: age at diagnosis; breast cancer; immunohistochemical subtype; mortality; prognosis.