Adjuvant chemotherapy for pT1-3N0-1 breast cancer patients with HR+, HER2- subtype: a propensity-score matched study with competing risk analysis.

Abstract

To wholly evaluate the prognostic value of CHT for pT1-3N0-1 breast cancer patients with HR+, HER2- subtype using the Surveillance, Epidemiology, and End Results (SEER) database. A total of 126,102 eligible cases diagnosed between January 2010 and December 2018 were included in the SEER database. A propensity-score matched (PSM) study with competing risk analysis was conducted. The Kaplan-Meier method was used to visualize the survival disparities between chemotherapy (CHT) and no CHT groups. The cumulative incidences of different subgroups were compared by Fine-Gray's test. Before PSM, patients in the CHT group had worse OS and CSS (both P < 0.001). After PSM, we were surprised that patients in the CHT group had a better OS than those in the no CHT group (HR 0.74, 95% CI 0.68-0.80, P < 0.001), while no significant survival disparities were observed for CSS (HR 1.00, 95% CI 0.89-1.12, P = 0.952). In the competing risk analysis, the OS disparities between the CHT and no CHT groups were mainly attributed to deaths of other causes (subdistribution HR [95% CI] 0.50 [0.44-0.57]). After adjusting for other competitive risk events, there was no significant difference in cumulative death risk of breast cancer between the CHT and no CHT groups (subdistribution HR [95% CI] 1.01 [0.90-0.1.13]). The present study is the first, to our knowledge, to wholly evaluate the prognostic value of CHT for pT1-3N0-1 breast cancer patients with HR+, HER2- subtype using a propensity-score matched study with competing risk analysis. All pT1-3N0-1 breast cancer patients with HR+, HER2- subtype do not benefit from CHT. Genetic testing may be the only effective tool to determine the need for CHT at the present.