Prognostic Factors for Survival in Patients with Oral Cavity Cancer: A Comparison of the Netherlands and Taiwan Using Privacy-Preserving Federated Analyses

Abstract

Background: The difference in incidence of oral cavity cancer (OCC) between Taiwan and the Netherlands is striking. Different risk factors and treatment expertise may result in survival differences between the two countries. However due to regulatory restrictions, patient-level analyses of combined data from the Netherlands and Taiwan are infeasible. Methods: We implemented a software infrastructure for federated analyses on data from multiple organisations. We included 41,633 patients with single-tumour OCC between 2004 and 2016, undergoing surgery, from the Taiwan Cancer Registry and Netherlands Cancer Registry. Federated Cox Proportional Hazard was used to analyse associations between patient and tumour characteristics, country, treatment and hospital volume with survival. Findings: Five factors showed differential effects on survival of OCC patients in the Netherlands and Taiwan: age at diagnosis, stage, grade, treatment and hospital volume. The risk of death for OCC patients younger than 60 years, with advanced stage, higher grade or receiving adjuvant therapy after surgery was lower in the Netherlands than in Taiwan, but patients older than 70 years, with early stage, lower grade and receiving surgery alone in the Netherlands were at higher risk of death than those in Taiwan. The mortality risk of OCC in Taiwanese patients treated in hospitals with higher hospital volume (≥50 surgeries per year) was lower than in Dutch patients. Interpretation: In this study, we conducted analyses without exchanging patient-level information, overcoming barriers for sharing privacy sensitive information. We found that the outcomes of patients treated in the Netherlands and Taiwan were slightly different after controlling for other prognostic factors. Funding Statement: This work is supported by grants from the Health Promotion Administration, Ministry of Health and Welfare, Taiwan (tobacco control and health care funds). Declaration of Interests: None. Ethics Approval Statement: This study was approved by the Data Release Review Board of the Health Promotion Administration, Ministry of Health and Welfare in Taiwan, which waived the requirement for informed consent.