Analysis of prognostic factors and survival outcomes for patients with T1N0 HER2-positive infiltrating ductal carcinoma of the breast: A real-world study with long-term follow-up.

Abstract

e12530 Background: The optimal adjuvant systemic treatment and prognostic factors for patients with T1N0 HER2-positive infiltrating ductal carcinoma (IDC) of the breast are still unclear. We conducted a real-world study in China to identify potential prognostic factors in this low-risk population, and to characterize survival outcomes of patients treated with different adjuvant strategies. Methods: We included patients with T1N0 HER2-positive IDC of the breast who were treated at the Cancer Hospital, Chinese Academy of Medical Sciences from April 2010 to April 2017. We performed Cox multivariate analysis to identify potential prognostic factors for invasive disease-free survival (IDFS). We also compared survival outcomes of 1) patients treated with adjuvant chemotherapy alone, or chemotherapy plus trastuzumab (Chemo+T), or observation only; 2) patients receiving adjuvant anthracycline (AC)-based and non-AC regimens, both combined with trastuzumab. Inverse probability of treatment weighting (IPTW) propensity score was used to reduce the selection bias. Results: Overall, 692 consecutive patients with pT1N0 HER2-positive IDC of the breast were included. The median follow-up was 78.0 months. Cox multivariate analysis demonstrated that age≤40 (HR = 2.62, 95%CI 1.39-4.92, P = 0.003) and T1c (HR = 2.35, 95%CI 1.17-4.74, P = 0.017) were associated with inferior IDFS, whereas ER+PR+ (HR = 0.44, 95%CI 0.26-0.77, P = 0.004) and adjuvant trastuzumab (HR = 0.21, 95%CI 0.12-0.35, P< 0.001) were associated with favorable IDFS. For adjuvant treatment, 104, 195, and 373 patients were identified for observation, chemotherapy alone, and Chemo+T, respectively. The IPTW-adjusted Kaplan-Meier analysis demonstrated that compared with observation and chemotherapy alone, the IDFS was significantly longer in the Chemo+T group ( P = 0.034 and < 0.001, respectively). Meanwhile, compared with observation, chemotherapy alone did not significantly prolong IDFS ( P = 0.424). For the comparison of AC-based vs. non-AC regimens, 141 patients were identified in the AC-based group and 227 in the non-AC group. The Kaplan-Meier analysis indicated that patients in both groups had similar IDFS ( P = 0.242). Conclusions: For patients with T1N0 HER2-positive IDC of breast, age≤40, T1c, ER+PR+, adjuvant trastuzumab are independent prognostic factors. We recommend adjuvant chemotherapy plus trastuzumab, especially for patients with T1c tumors. When used in combination with trastuzumab, non-AC regimens may have similar efficacy with AC-based regimens.