Abstract P2-08-19: Disparities in triple negative breast cancer survival in the United States by patient characteristics: A population-based study from SEER database, 2010 - 2015
Authors: Wang Zikun , Lu Zheyu , Kalra Maitri , Chen Zhongxue , Dong Yi 
Published: March 2020

Introduction: Efforts to improve the outcomes of triple negative breast cancer (TNBC) have been hampered by the inability to identify the key risk factors for prognosis. We focus solely on female TNBC and explored its survival by age, marital status, treatment and race. Data from Surveillance, Epidemiology and End Results Program (SEER) Database 18 of National Cancer Institute were used to assess TNBC survival by the above factors.

Results: A total of 26,413 female patients diagnosed with TNBC from 2010 to 2015 were included in the current study, including 15840 (60.0%) Non-Hispanic white women. The follow up time ranges: 0 to 83 months. Younger (≤ 49) and elderly (≥ 65) age is associated with poorer survival, with reference to middle age group (50-64). The breast cancer specific survival (BCSS) rate for the three age groups (≤ 49, 50-64 and ≥ 65) are 78.6%, 81.0% and 78.1%, respectively; hazard ratio (HR) (95% confidence interval [CI]): 1.17 (1.08-1.27) in ≤ 49 and 1.24 (1.15-1.34) in ≥ 65 patients, individually. We further categorized elderly group into two strata: aged 65 -74 (age group recommended by U.S. Preventive Services Task Force to have breast cancer [BC] screening) and ≥75 (not recommended for BC screening). Our data revealed that the BCSS rate of 65-74 cohort rises to 81.9%; HR (95% CI): 0.97 (0.88-1.07), not significantly different from group aged 50-64. In contrast, the ≥75 group, as against middle age cohort, has the worst BCSS rate of 71.6%; HR (95% CI): 1.74 (1.58-1.92). In patients ≥75, there is highest proportion of metastatic disease (2.9%) at diagnosis and advanced lymph node involvement (N2 + N3 = 11.9%); their percentage of receiving perioperative chemotherapy (CT) and radiation therapy (RT) is lowest across all age groups: 33.3% and 43.6%, respectively.

The mean age of single (never married), married and widowed patients at diagnosis was 52 ± 13, 56 ± 12 and 72 ± 11, respectively. The single cohort has the second worst BCSS rate of 76.1% [HR (95% CI): 1.46 (1.34-1.59)], in comparison with married women (BCSS rate of 81.6%). The BCSS rate of single patients is only better than that of widowed population (74.7%), who have significantly advanced age. Our analyses also showed that single patients have the highest percentage of Black women (37.7%) that are known to have unfavorable prognosis of TNBC. Also, single female patients have high proportion of large tumor (T3 + T4 = 18.5%, highest among all women in study) and metastatic disease (2.9%, secondary to widowed group only). Single group compared with married group, tends to have lower percentage of completing RT: 49.9% versus 53.4%, respectively.

Conclusion: Advanced age is associated with worse BCSS. However, discontinuation of BC screening may partly account for the phenomenon that ≥ 75-year-old patients lost survival benefits (i.e., highest metastatic disease at diagnosis and worst BCSS), that is maintained in patients aged 65-74, who are recommended for BC screening. Further, low adherence to receive or complete adjuvant therapy may attenuate the survival in elderly patients aged ≥ 75. The poor outcome in single women with relatively young age indicates that both biological and socioeconomic factors and their interactions (e.g., high proportion of black women and low proportion of receiving RT) may influence TNBC prognosis. Our findings suggest a greater need for early and extended BC screening in the above two populations.

Citation Format: Zikun Wang, Zheyu Lu, Maitri Kalra, Zhongxue Chen, Yi Dong. Disparities in triple negative breast cancer survival in the United States by patient characteristics: A population-based study from SEER database, 2010 - 2015 [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-08-19.