Abstract P3-08-02: Validation of the online prediction tool PREDICT v. 2.0: A large population-based study in the Netherlands
Authors: van Maaren MC , van Steekbeek CD , Pharoah PDP , Witteveen A , Sonke GS , Strobbe LJA , Poortmans PMP , Siesling S 
Published: February 2018

Abstract
Background
This study aimed to validate the online prediction tool PREDICT version 2.0 on a large population-based cohort in the Netherlands. Separate analyses were performed to study its validity in specific prognostic subgroups.
Methods
All women diagnosed with non-metastasised primary invasive breast cancer in 2005, who received surgery as part of their treatment, were selected from the nationwide Netherlands Cancer Registry (NCR). The predicted 5-year and 10-year overall survival (OS) from PREDICT were compared with the observed OS from the NCR, for the overall cohort (separated by ER- and ER+ patients) and for predefined subgroups based on age, T stage, N stage, presence of micrometastases, grade, HER2 status, type of surgery, use and type of adjuvant systemic therapy and generation chemotherapy. Our a priori assumption was that PREDICT accurately predicted OS whenever the differences between predicted and observed outcomes were within a range of 5%, since a difference of 5% or more was considered as clinically relevant. The discriminatory accuracy and goodness-of-fit were determined using the area under the receiver operating characteristic curve (AUC) and the Chi2-test, respectively.
Results
Our study population consisted of 8,834 patients. Discriminatory accuracy for 5-year OS was good with an AUC of 0.80. For ER- and ER+ patients, the AUCs were 0.75 and 0.79, respectively. Predicted 5-year OS differed from observed by -1.4% (p=0.14) in the entire cohort, by -4.9% (p=0.02) in ER- patients and -0.7% (p=0.53) in ER+ patients. In all predefined subgroups no statistically significant differences between predicted and observed events were observed.
Discriminatory accuracy for 10-year OS was good with an AUC of 0.78 for the overall cohort, 0.76 for ER- patients and 0.78 for ER+ patients. Predicted 10-year OS differed from observed by -1.0% (p=0.27) in the entire cohort, by -5.3 (p=0.01) in ER- patients and -0.1% (p=0.92) in ER+ patients. Ten-year OS was overestimated in patients ≥75 years (6.3%, p=0.00), and underestimated in T3 stage (-13.%, p=0.00) and in patients treated with both endocrine therapy and chemotherapy (-6.6%, p=0.02).
Conclusion
PREDICT accurately predicts 5-year OS in the entire Dutch validation population, and in all predefined subgroups. However, 10-year OS was overestimated for patients ≥75 years, and underestimated for T3 stage and patients treated with both endocrine therapy and chemotherapy. Given PREDICT's intentions to guide treatment decision-making, PREDICT may serve as a reliable prediction tool for the Dutch breast cancer population, but especially in patients ≥75 years, 10-year OS predictions should be interpreted with care.
Citation Format: van Maaren MC, van Steekbeek CD, Pharoah PDP, Witteveen A, Sonke GS, Strobbe LJA, Poortmans PMP, Siesling S. Validation of the online prediction tool PREDICT v. 2.0: A large population-based study in the Netherlands [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-08-02.