P2-12-16: HER2 Expression Is the Major Risk Factor for Recurrence in pT1a-b,N0 Breast Cancer: A French Regional Population-Based Study of 671 Patients.

Abstract Background: To evaluate the prognostic impact of HER2 overexpression in patients with pT1a-b, node negative, breast cancers. Patients and Methods: A population of1127 patients whose diseases were staged as pT 1a-b, pN0 and who were treated in the Languedoc-Roussillon (ONCO LR Southern French regional network) from 1999 to 2004, was identified. 95% of patients had conservative management, no patient received adjuvant trastuzumab, 5% received chemotherapy and 80% anti-estrogen endocrine therapy. HER 2 status was retrospectively assessed by immunohistochemistry in 671 patients (122 pT1a/549 pT1b). Kaplan-Meier method was used to estimate disease-free survival (DFS). Cox proportional hazard models were used to determine associations between HER2 status and disease-free survival adjusting on variables significantly linked to it. Results: 9-year Overall survival was 95%. HER2 overexpression (3+) was observed in 5.2% of the patients (n=35). HER2 3+ category was most frequently identified in the following sub groups: pT1a lesion (12.3% vs 3.6%; p: 0.0001), mastectomies (14% vs 4.4%; p:0.023), Grade 2–3 (91% vs 50%; p<0.0001), estrogen receptor (ER) negative (−) tumors (57% vs 30%; p<0.0001), progesterone receptor (PR) - tumors (74% vs 42%; p: 0.0002). HER2 3+ was less frequent with adjuvant hormonal treatment (43% vs 80%; p<0.0001). 33 relapse (5%) were observed with a median follow-up of 6.4 years (range, 0.3 to 9.9 years). The 5-year DFS rates were 78% and 95% in patients with HER2−positive and HER2−negative tumors, respectively (p:0.017). According to the immunohistochemical phenotype DFS5 were 95%, 94%, 85%, 73.6% for ER+/PR+/HER2− (n:502/75%), ER-/PR-/ HER2− (n:134/20%), ER+/PR+/HER2 3+ (n:15/2%) and ER-/PR-/ HER2 3+ tumors (n:20/3%), respectively (p:0.02). In univariate analysis, HER2 positive tumors (p:0.017), phenotype classification (p:0.02) and adjuvant treatment (p:0.013) were significant prognostic factors. In multivariate analysis, only patients with HER2 3+ tumors had higher risks of recurrence (hazard ratio [HR], 2.41; 95% CI: [1.06−5.53]; p<0.05) than those with HER2 -tumors. Discussion: Node-negative, pT1a-b, breast cancer patients overexpressing HER2 have a significant risk of recurrence at 6 years median follow-up. In our series of small breast tumors, HER2 status seems to be a better prognostic factor than ER status. In patients with hormone receptor-positive diseases, HER2 positivity is associated with a worse DFS despite an anti-estrogen treatment. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-16.