[Cancer screening: blessing or curse?].

Cancer screening seems intuitively logical: early detection to prevent worse outcomes. However, this article reveals the complexity behind this assumption. Cancer's linear growth model- on which early detection was based - proves outdated. Cancers grow at vastly different rates; some even stop or disappear spontaneously. The main problem is overdiagnosis: in Dutch breast cancer screening, approximately 2,000 women are treated annually for cancers that would never cause symptoms. Epidemiological data show a persistent increase in stage I cancers without a decline in stage IV cases - a sign of overdiagnosis. Screening has a Janus face: on one hand life-saving potential, on the other unnecessary treatments with side effects. Effectiveness must be proven through randomized trials that reduce cancer-specific and overall mortality. Citizens deserve honest information about this balance between intuition and scientific evidence. Core message: Screening only works if it reduces mortality, not merely by finding more cancers.