Abstract P5-08-47: Clinical outcome of pathological T1N0 breast cancer according to the hormone receptor and HER2 status and adjuvant therapy

Abstract

Abstract Background: The outcome of T1N0 breast cancer is relatively good, however, a subpopulation of this stage has a high population of relapse. It is important to clarify the factors associated with the outcome in order to determine the adequate adjuvant systemic therapy for T1N0 breast cancer. Aims: To investigate the prognosis of pathological T1N0 (pT1N0) breast cancer by receptor (estrogen receptor; ER, progesterone receptor; PgR, human epidermal growth factor receptor 2; HER2) status and adjuvant systemic therapy, and thus to identify the factors associated with the outcome. Methods: Among 2164 women who underwent surgery for primary breast cancer in our department, 925 had pathological T1N0 tumors (130 T1a, 234 T1b and 561 T1c). The associations between clinicopathological characteristics, adjuvant therapy and relapse-free survival (RFS) were examined Results: Of 908 patients with known hormone receptor (HR; ER and PgR) and HER2 status, 675, 79, 64 and 90 had HR+/HER2-, HR+/HER2+, HR-/HER2+ and HR-/HER2- (triple negative; TN) tumors, respectively. The prognosis of patients with T1c tumors was significantly poorer than that of the patients with T1a and T1b tumors (5-year DFS of T1a, T1b and T1c: 97.5%, 97.9%, 94.5%, p=0.0201). HR+/HER2- subtype was significantly associated with better prognosis than other subtypes (5-year DFS: 96.9% vs. 93.6%, p=0.0194). Patients younger than 40 year old or older than 74 years old had significantly shorter PFS (p=0.0039). Lymphovessel invasion (ly), high histological grade (HG2, 3) were associated with poor outcome in all cohort (p=0.0026, p=0.0356). In HR-positive tumors, ly, high HG and omission of the adjuvant endocrine therapy were associated with shorter RFS (p=0.0009, p=0.0306 and p=0.0016, respectively). Adjuvant chemotherapy was not associated with RFS regardless of HR and HER2 status. However, in T1c with nuclear grade (NG) 3 tumors, use of the adjuvant chemotherapy was associated better prognosis. The prognosis of patients with HER2+ tumors was not significantly different among patients with or without trastuzumab in this cohort. Conclusion: In spite of the excellent prognosis of pT1N0 breast cancer, adjuvant endocrine therapy is important for patients with HR+ tumors. However, the use of adjuvant chemotherapy or trastuzumab did not significantly improve the prognosis. Thus, the indication of chemotherapy or anti-HER2 therapy should be determined in consideration of the several prognostic factors for pT1N0 breast cancer. Citation Format: Tokunaga E, Akiyoshi S, Koga C, Nakamura Y, Taguchi K, Ishida M, Ohno S. Clinical outcome of pathological T1N0 breast cancer according to the hormone receptor and HER2 status and adjuvant therapy. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-08-47.