Overdiagnostikk – eksemplifisert ved mammografiscreening
DOI:
https://doi.org/10.5324/nje.v30i1-2.4981Sammendrag
Norsk sammendrag
Hovedmålsettingen med organisert mammografiscreening er å oppdage brystkreft i et tidlig stadium og dermed redusere sykelighet og dødelighet av sykdommen. En ulempe er overdiagnostikk. Verdens helseorganisasjons kreftforskningsinstitutt definerer overdiagnostikk i mammografiscreening som brystkreft som ikke ville blitt diagnostisert i kvinnens levetid dersom hun ikke hadde deltatt i screening. Vi kan ikke identifisere hvilke svulster som er overdiagnostiserte eller nøyaktig tallfeste omfanget av overdiagnostikk i mammografiscreening. Dersom vi analyserer data fra store grupper, kan vi gi et anslag på omfanget. Resultatet vil være avhengig av blant annet beregningsmetode, kontrollgruppe, oppfølgingstid, og hva slags type data som benyttes (individdata versus aggregattall). Selv om subtyper av brystkreft med ulik prognose kan defineres, kan vekstmønsteret innenfor samme subtype endres over tid, og det er derfor ikke mulig på diagnosetidspunktet å identifisere hvilke svulster som er overdiagnostiserte og ikke trenger behandling. Alle kvinner som får diagnostisert brystkreft tilbys derfor behandling. Begrepet overdiagnostikk er sammensatt og vanskelig å forstå. I noen sammenhenger brukes det som et paraplybegrep for ulike fenomener som for eksempel feildiagnoser, falskt positive screeningresultater eller overbehandling. Overdiagnostikk i mammografiscreening omfatter ikke feildiagnostikk eller falskt positive screeningresultater. Økt kunnskap i befolkningen og bruk av mer avanserte undersøkelsesteknikker gjør at flere brystkreftsvulster nå oppdages i et tidlig stadium og dermed øker risikoen for overdiagnostikk og overbehandling. Nye behandlingsmetoder reduserer brystkreftdødeligheten, også ved avansert sykdom, men ofte med bi- og seneffekter. Målet er mer presise screening- og diagnosemetoder, og mer persontilpasset behandling enn vi har i dag. Likevel er nok noe overdiagnostikk og overbehandling prisen vi må betale for å redde kvinner fra å dø av brystkreft.
English summary
The goal of organized mammographic screening is early detection of breast cancer and thereby to reduce disease-specific morbidity and mortality. One disadvantage is overdiagnosis. The World Health Organization's International Agency for Research on Cancer defines overdiagnosis in mammographic screening as the diagnosis of a breast cancer as a result of screening that would not have been diagnosed in the woman’s lifetime if screening had not taken place. We cannot identify which tumors are overdiagnosed or accurately quantify the extent of overdiagnosis in mammographic screening. Analyzing data from large groups will give an estimate, but the result will depend, among other things, on the calculation method, control group, follow-up time, and type of data used (individual data versus aggregate numbers). Although subtypes of breast cancer with different prognosis can be defined, the growth patterns within the same subtype can change over time, and it is therefore not possible at the time of diagnosis to identify which tumours are overdiagnosed and do not require treatment. All women who are diagnosed with breast cancer are thus offered treatment. The term overdiagnosis is complex and difficult to understand. In some contexts, it is used as an umbrella term for various phenomena such as misdiagnosis, false positive screening results or overtreatment. Overdiagnosis in mammographic screening does not include misdiagnosis or false positives. Increased knowledge in the population and the use of more advanced examination techniques means that more breast cancer tumours are now detected at an early stage and thus increases the risk of overdiagnosis and overtreatment. New treatment methods reduce breast cancer mortality, also for advanced disease, but often at the cost of side and late effects of the treatment. The future goal is more precise screening and diagnostics, and more personalized treatment. Nevertheless, some overdiagnosis and overtreatment is probably the price we have to pay to save women from dying of breast cancer.
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Opphavsrett 2022 Solveig Hofvind
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