Background: Due to increasing detection and screening activities and incidental findings, the incidence of thyroid cancer has increased in several countries during the last decades. However, it is possible that this increase reflects growing detection of indolent thyroid cancer forms, indicating potential overdiagnosis. We analyzed secular trends in the incidence and mortality of thyroid cancer, as well as of thyroid surgery, in Switzerland to assess for overdiagnosis and overtreatment.
Methods: We used primary invasive thyroid cancer cases (C73, International Classification of Diseases for Oncology) recorded between 1998-2012 in all population-based cantonal cancer registries. Cancer cases were classified by histological subtype (papillary vs. non-papillary) and stage (early vs. advanced) according to oncology guidelines using the TNM classification. We assessed thyroid cancer-specific mortality. We also analyzed trends in thyroid surgery between 2001-2012 using data from the Swiss Federal Statistical Office's hospital statistics.