Immunohistochemically Defined T1N0 Breast Cancer Subgroups Have Different Clinical Outcomes. A Retrospective Turkish Oncology Group Study.

Abstract

Abstract Introduction: T1N0 breast cancer (BC) has a very favorable outcome therefore the need of adjuvant systemic therapy is controversial. Molecular profiling studies identified BC subtypes with distinct clinical outcomes. We planned to determine whether immunohistochemically (IHC) defined subgroups of T1N0 BC patients have different clinical outcomes. Methods: Medical records of pts with T1N0 BC and known ER, PR and Her-2 status who have been treated between 1998-2008 were reviewed. Patients with bilateral disease, who had adjuvant trastuzumab therapy were excluded. Clinical/pathological, treatment characteristics were recorded and patients were subdivided into four BC subtypes: triple negative (ER, PR, HER2 negative), HER2 (ER and PR-negative, HER2-positive), luminal B (ER-positive and/or PR-positive, HER2-positive), and luminal A (ER and/or PR-positive and HER2-negative). Her-2 positivity was defined as IHC 3+ or FISH positive IHC2 2+. Survival outcome of the IHC defined subgroups were analyzed the Kaplan-Meier method and compared with the log-rank test. Results: A total of 1035 pts have been identified from 17 Medical/Radiation Oncology centers in Turkey. Median age was 51 and median follow up was 39 months. Forty-four % of patients were premenopausal, 55% had left breast involved, 73% had breast conserving surgery, 81% had invasive ductal carcinoma. T1a,b,c tumors were 7%, 30%, 63% ; grade 1,2,3 tumors were 20%, 53%, 27% respectively. HER2 was 2 + in 59 (6%) and 3 + in 111 (11%) tumors. Twelve % tumors were triple negative. Thirty-seven % patients had adjuvant chemotherapy; 80 % had adjuvant endocrine therapy 73% had adjuvant radiotherapy. Five-yr DFS and OS of the whole group were 92% and 99% respectively. So far, 19 pts had local and 24 pts had distant metastases, 4 pts had secondary cancers, 6 patients contralateral BC and 11 patients died (7/11 pts died from breast cancer). Classification based on ER, PR and Her-2 status had significant impact on 5-yr DFS (p:0.00) and OS (p:0.00). The 5-yr DFS and OS were 84%;74%;%;94% and 96%;83%;100%;99% respectively for triple negative, HER2, luminal B, and luminal A subgroups respectively. Hormone receptor and triple negative status were the two other parameters affecting survival outcome significantly (p:0.00, p: 0.007) in the univariate analyses. Conclusion: Most patients with T1N0 disease have generally a favorable clinical outcome, however even within this very early stage of BC there are subgroups with diverse clinical outcomes. Despite our short follow up with low number of events, we found that Her-2 positive and triple negative T1N0 BC have poor clinical outcomes compared to luminal T1N0 subgroups and therefore they might need special concern with respect to adjuvant systemic therapy. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3167.