Risk estimations and treatment decisions in early stage breast cancer: agreement among oncologists and the impact of the 70-gene signature

Clinical decision-making in patients with early stage breast cancer requires adequate risk estimation by medical oncologists. This survey evaluates the agreement among oncologists on risk estimations and adjuvant systemic treatment (AST) decisions and the impact of adding the 70-gene signature to known clinico-pathological factors. Twelve medical oncologists assessed 37 breast cancer cases (cT1-3N0M0) and estimated their risk of recurrence (high or low) and gave a recommendation for AST. Cases were presented in two written questionnaires sent 4 weeks apart. Only the second questionnaire included the 70-gene signature result. The level of agreement among oncologists in risk estimation (κ=0.57) and AST recommendation (κ=0.57) was 'moderate' in the first questionnaire. Adding the 70-gene signature result significantly increased the agreement in risk estimation to 'substantial' (κ=0.61), while agreement in AST recommendations remained 'moderate' (κ=0.56). Overall, the proportion of high risk was reduced with 7.4% (range: 6.9-22.9%; p <0.001) and the proportion of chemotherapy that was recommended was reduced with 12.2% (range: 5.4-29.5%; p <0.001). Oncologists' risk estimations and AST recommendations vary greatly. Even though the number of participating oncologists is low, our results underline the need for a better standardisation tool in clinical decision-making, in which integration of the 70-gene signature may be helpful in certain subgroups to provide patients with individualised, but standardised treatment