Harms and Benefits of Cancer Screening.

In recommending and offering screening, health services make a health claim ('it's good for you'). This article considers ethical aspects of establishing the case for cancer screening, building a service programme, monitoring its operation, improving its quality and integrating it with medical progress. The value of (first) screening is derived as a function of key parameters: prevalence of the target lesion in the detectable pre-clinical phase, the validity of the test and the respective net utilities or values attributed to four health states-true positives, false positives, false negatives and true negatives. Decision makers as diverse as public regulatory agencies, medical associations, health insurance funds or individual screenees can legitimately come up with different values even when presented with the same evidence base. The main intended benefit of screening is the reduction of cause-specific mortality. All-cause mortality is not measurably affected. Overdiagnosis and false-positive tests with their sequelae are the main harms. Harms and benefits accrue to distinct individuals. Hence the health claim is an invitation to a lottery with benefits for few and harms to many, a violation of the non-maleficence principle. While a public decision maker may still propose a justified screening programme, respect for individual rights and values requires preference-sensitive, autonomy-enhancing educational materials-even at the expense of programme effectiveness. Opt-in recommendations and more 'consumer-oriented' qualitative research are needed.