Abstract P3-14-12: High Risk of Recurrence in Japanese Patients with HER2-Positive T1N0 Breast Cancer

Abstract

Abstract Background: The necessity of adjuvant trastuzumab therapy for patients with T1N0M0 tumors remains controversial. The objective of this study is to determine the risk of recurrence in Japanese women with T1N0 HER2- positive tumors compared with HER2-negative tumors. Methods: Among 1,180 patients with breast cancers diagnosed at our institution between 2001 and 2007, we reviewed 464 T1N0M0 diseases in which HER2 status was evaluated by IHC or gene amplification, who had not received trastuzumab in the adjuvant setting. Recurrence free survival (RFS) was estimated using the Kaplan-Meier method and compared with the log-rank test. Cox proportional hazards models were used to determine the association of each group with the risk of recurrence. Results: Seventy-nine (17%) of 464 patients had HER2-positive tumors and remaining 385 (83%) were HER2-negative diseases. Patients who had HER2-positive tumors tended to be younger (P=0.015), have more hormone receptor-negative tumors (P<0.001), and have higher histological grade (P<0.001). At a median follow-up of 46 months, 18 patients had experienced recurrences. The 5-year recurrence-free survival (RFS) rates were 88.2% and 97.2% in patients with HER2-positive and HER2-negative tumors, respectively (P<0.001). In patients with T1bN0 tumors and T1cN0 tumors, HER2-positive group had worse RFS than HER2-negative group (P=0.004 and P=0.002, respectively), while there were no differences in the RFS between patients with T1aN0 HER2-positive and HER2-negative tumors (P=0.835). In a multivariate analysis, HER2 status was identified as one of the independent risk factors to predict RFS in patients with T1N0M0 breast cancers (hazard ratio 5.23; 95% CI, 2.07 to 13.21; P<0.001). Conclusion: Japanese women with T1bcN0M0 HER2-positive breast cancer have a significant high risk of recurrence, and adjuvant trastuzmab therapy should be considered for those patients. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-14-12.