Comment on: Wiser et al. Ovarian cancer in Switzerland: incidence and treatment according to hospital registry data. Swiss Med Wkly.2018;148:w14647

Wieser and colleagues, in a study published in Swiss Medical Weekly in July 2018, compared incidence rates of ovarian cancer derived from the cantonal cancer registries (CCRs) as published by the National Institute for Cancer Epidemiology and Registration (NICER) with those derived from the hospital discharge data compiled by the Swiss Federal Statistical Office. The authors observed a substantial difference between these two estimates. The average age-adjusted ovarian cancer incidence rate was 14.6 per 100,000 women per year over the period 2004–2012 compared with a rate of 11.3 per 100,000 women per year reported by NICER for the same period [1]. The authors argue that the figure provided by NICER is probably an underestimation of the true figure because cancer registry data are based on voluntary information on new cases from clinicians.With our response, we show that this conclusion is not correct and the observed high rate of ovarian cancer in hospital discharge data is an artefact, probably arising from incorrect coding of non-malignant ovarian tumours. Further, we explain the purpose of epidemiological cancer registries and their difference from routinely collected discharge data.