Abstract P2-10-42: Gene expression profiling to predict the risk of locoregional recurrence in breast cancer

Abstract

Abstract Background The 70-gene signature (Mammaprint™) has been developed to predict the risk of distant metastases in breast cancer and select those patients who will have benefit in survival from adjuvant treatment. Aside from distant metastases, the development of locoregional recurrence is a significant predictor of survival. Given the strong association between locoregional recurrence and distant recurrence, we hypothesize that the 70-gene signature will be predictive of locoregional recurrence as well. Methods We updated follow-up and radiotherapy details for all 1053 unique breast cancer patients treated at the NKI-AVL who previously participated in various 70-gene signature validation studies. Diagnosis was between 1984 and 2006. All patients were primarily treated surgically with either breast-conservation therapy or mastectomy. Adjuvant treatment consisted of radiotherapy, chemotherapy and/or endocrine therapy as indicated. Known risk factors for locoregional recurrence including age, tumor free resection margins, tumor size, grade, ER status, Her2 status, nodal irradiation and tumor bed boost were included in our analysis in addition to the 70-gene signature result. Results Through 10 years of follow-up, 80 locoregional recurrences occurred. Patients with a 70-gene signature high risk result (n = 492) had a locoregional recurrence risk of 8.8% (95%CI: 6.3–11.3) at 5 years and 13.5 % (95%CI: 10.2–16.8) at 10 years, which was 2.6% (95%CI: 1.2–4.0) at 5 years and 5.7% (95%CI:3.5–7.9) at 10 years for patients with a low risk 70-gene signature (n = 561)(Logrank: p < 0.0001). Accordingly, patients with a high risk 70-gene signature had an approximately 3 times higher risk of locoregional recurrence than patients with a low risk 70-gene signature (univariable hazard ratio (HR) 2.89; 95%CI: 1.80–4.63). Adding the 70-gene signature to a Cox proportional hazard model containing age, size, grade, ER status, involvement of axillary lymph nodes, surgical treatment and adjuvant treatment (radiotherapy, chemotherapy and/or endocrine therapy), significantly improved the model (likelihood ratio: p = 0.007). In that model, the multivariable HR for high versus low 70-gene signature risk was 2.27 (95%CI: 1.24–4.15). Conclusion The 70-gene signature is able to predict the risk of locoregional recurrence, independent of known risk factors. Using the 70-gene signature may help in selecting those patients who will benefit from extensive adjuvant treatment. Additionally, the 70-gene signature may also select a group of patients at a low risk of locoregional recurrence who may be cured with limited local treatment alone. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-42.