24 september 2010: Bron ANP en Medscape
Het regelmatig screenen van vrouwen op eventueel borstkanker d.m.v. mammografie blijkt minder voordeel op te leveren op het uiteindelijk voorkomen van overlijden aan borstkanker dan altijd is aangenomen en voorspeld. Blijkt ook nu weer uit een groot Noors bevolkingsonderzoek. De verhouding kosten en effectiviteit van het bevolkingsonderzoek naar ontstaan van borstkanker dat in Nederland om de twee jaar plaatsvind komt hiermee wereldwijd steeds meer onder druk te staan. Uit dit Noors onderzoek blijkt dat het positieve effect op een succesvolle behandeling van borstkanker als er borstkanker in een vroeg stadium wordt ontdekt 10% bedraagt. Maar de mammografie zou daarvan slechts 1/3 voor zijn rekening nemen. De andere 2/3 zou het effect zijn van betere diagnostiek, betere behandelingen en hogere individuele bewustwording van de vrouw die ook regelmatig zelfonderzoek zou doen. Hier de resultaten uit het Noors onderzoek. Bron: Medscape
The Norwegian Protocol
In the Norwegian study, 40,075 women received a diagnosis of breast cancer from 1986 to 2005. Of the 4791 women (12%) who died, 423 (9%) received their diagnosis after the screening program was introduced.
The study consisted of 4 groups of women: a screening group of women who lived in counties that had a screening program (1996 to 2005); a nonscreening group of women who lived in counties that did not have a screening program (1996 to 2005); and 2 historic groups from before the implementation of the screening program (1986 to 1995) that mirrored the screening and nonscreening groups.
The analyses showed that the death rate in the screening group was 18.1 per 100,000 person-years, compared with 25.3 per 100,000 person-years in the historic screening group, for a difference of 7.2 deaths per 100,000 person-years (rate ratio, 0.72; 95% confidence interval , 0.63 - 0.81; P < .001). This amounted to a relative reduction of 28%.
In the nonscreening group, the mortality rate was 21.2 per 100,000 person-years, compared with 26.0 per 100,000 person-years in the historic nonscreening group. This amounted to a difference of 4.8 deaths per 100,000 person-years (rate ratio, 0.82; 95% CI, 0.71 - 0.93; P < .001), for a relative reduction of 18%.
Lower Than Previously Seen
Previous studies with a follow-up period of 10 years or less have shown a relative reduction in the rate of death from breast cancer (from 6.4% to 25.0%). The mortality reduction in the current study is also much lower than the 15% to 23% estimated by the US Preventive Services Task Force.
There are several possible explanations for these differences, explained Dr. Kalager. "It is quite plausible that today, the effect of increased breast cancer awareness and improved therapy have outweighed the effect of screening on reducing mortality from breast cancer."
"Thus, screening may be less important than it was 20 years ago," she added. "Further, our study is a population-based cohort study, and sometimes results from the randomized controlled trials are not reached in a population setting."
Even though the reduction in mortality was less than expected, Dr. Kalager emphasized that the screening program reduced death from breast cancer for women 50 to 69 years of age.
Importance of Optimized Care
Another surprise was that in women who were in the nonscreening age group (70 to 84 years), the reduction in breast cancer mortality (about 8%) was largely the same as in the screening group (women 50 to 69 years of age).
"This can be explained by treatment by the multidisciplinary teams of highly specialized radiologists, radiologic technologists, pathologists, surgeons, oncologists, and nurses that managed the care of the patients," Dr. Kalager said.
Thus, the 10% reduction we found in women in the screening age group "is attributed to both the mammograms and management by multidisciplinary teams," she said.
The program began in Norway in 2005, and all women 50 to 69 years of age received an invitation to undergo screening mammography every 2 years. Each county in Norway was required to establish multidisciplinary breast cancer management teams and breast units before enrolling in the national screening program, Dr. Kalager explained.
For women outside that age group (the nonscreening cohort), the change in mortality could be related only to the establishment of multidisciplinary teams, she said. "The importance of optimized patient care is often missed."
Gerelateerde artikelen
- Screening van borstkanker (mammografie) levert minder voordeel op in uiteindelijke genezing van borstkanker dan voorspeld, aldus groot Noors bevolkingsonderzoek
- Regelmatig screenen zou de kans op overlijden aan borstkanker significant verminderen. Euforie hierover is wel gebaseerd op klein en niet gerandomiseerd onderzoek en lijkt van weinig betekenis
- Screening van borstkanker via een mammografie geeft geen enkel positief effect op uiteindelijke overlevingscijfers blijkt uit 25 jarige studie bij totaal 89.835 vrouwen in de leeftijd van 40 tot 59 jaar in Canada.
Plaats een reactie ...
Reageer op "Screening van borstkanker (mammografie) levert minder voordeel op in uiteindelijke genezing van borstkanker dan voorspeld, aldus groot Noors bevolkingsonderzoek"