The Symphony Triple A Study: Using Symphony in Treatment Decisions Concerning Adjuvant Systemic Therapy

Rationale: Prediction of prognosis in patients with breast cancer is important to determine the indication for adjuvant chemo-, endocrine- and immunotherapy. Apart from the clinicopathological parameters incorporated into the Adjuvant!Online predictive model, the validated 70-gene signature MammaPrint® is predictive of outcome too. MammaPrint® is advised in the current Dutch CBO guideline (2012) for hormone receptor positive, invasive ductal breast cancer in individual cases when there is 'doubt' about the indication for adjuvant chemotherapy based on traditional prognostic factors. In the present study MammaPrint® is used in this CBO 2012 guideline defined group of patients as an additional test for decision-making for adjuvant chemotherapy. Objective: To assess the impact of MammaPrint® on clinical decision making regarding the administration of adjuvant chemotherapy in the CBO 2012 guideline defined group of hormone receptor positive invasive ductal carcinoma patients when there is doubt about the indication for adjuvant chemotherapy based on traditional prognostic factors. The influence of various factors and the impact of MammaPrint® in predefined subgroups will be analyzed too. Data from a national registry regarding adjuvant systemic treatment in patients with similar clinicopathological characteristics in whom MammaPrint® was not used will be obtained to provide a control group. Hypothesis: In the group of patients where national guidelines advocate using systemic therapy but doctors are ambivalent in treating patients with adjuvant chemotherapy, it is hypothesized that using MammaPrint® as an additional test will change the indication for adjuvant therapy in a substantial proportion of patients resulting in at least 10% less patients who receive adjuvant chemotherapy. Thus, in the study group at least 10% less patients will receive chemotherapy when compared to a contemporary group of patients with similar clinicopathological characteristics but withou