Effect of Screening Mammography on Breast-Cancer Mortality in Norway (original) (raw)
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Breast cancer mortality in Norway after the introduction of mammography screening
International Journal of Cancer, 2013
An organized mammography screening program was gradually implemented in Norway during the period 1996-2004. Norwegian authorities have initiated an evaluation of the program. Our study focused on breast cancer mortality. Using Poisson regression, we compared the change in breast cancer mortality from before to during screening in four counties starting the program early controlling for change in breast cancer mortality during the same time in counties starting the program late. A follow-up model included death in all breast cancers diagnosed during the follow-up period. An evaluation model included only breast cancers diagnosed in ages where screening was offered. The study group had been invited for screening one to three times and followed for on average of 5.9 years. In the follow-up model, 314 breast cancer deaths were observed in the study group, and 523, 404 and 638, respectively, in the four control groups. The ratio between the changes in breast cancer mortality between early and late starting counties was 0.93 (95% confidence interval [CI] 0.77-1.12). In the evaluation model, this ratio was 0.89 (95% CI: 0.71-1.12). In Norway, where 40% of women used regular mammography prior to the program, the implementation of the organized mammography screening program was associated with a statistically nonsignificant decrease in breast cancer mortality of around 11%.
Mammography activity in Norway 1983 to 2008
Acta Oncologica, 2011
Background. In Norway, an organized screening mammography program, the Norwegian Breast Cancer Screening Program (NBCSP) started in four counties in 1996 and became nationwide in 2004. We collected data on pre-program screening activity, and in view of this activity we evaluated the potential impact of the program on breast cancer mortality in Norway. Methods. We searched data sources on mammography activity in Norway. Three data sources reported on examination activity, and two on self-reported examinations. We aimed at calculating annual number of women examined by mammography from 1983 to 2008, and coverage rate in program and non-program Norwegian counties. Results. The annual number of women examined increased from 5000 in 1983 to 110 000 in 1993 to reach its maximum of 131 000 in 2002, excluding program examinations. The annual number of women examined in the organized program increased from 1996 to a steady state about 190 000 in 2004. Prior to start of the organized program, 40% of women in target age groups reported to have had mammography examination. During the years 1996 -2002, 64% of fi rst participants in the organized program reported to have been examined previously. Assuming that the Norwegian program would in absence of prior screening have decreased breast cancer mortality by 25%, and that the activity in-and outside the organized program were equally effective, the measured effect of the organized program would under actual circumstances be a reduction of 11%. Conclusion. The example of Norway illustrates that although monitoring of screening outcome is highly warranted, this may be seriously jeopardized if use of mammography examinations was widespread prior to implementation of an organized program.
The Cancer Registry of Norway – “a ground for scientific harvesting”
Norsk Epidemiologi
The Cancer Registry of Norway (CRN) has been important in registry-based research in Norway for decades. The use of CRN in combination with other population-based registries and health surveys have been the basis for numerous research projects, which has contributed to fill important knowledge gaps. Researchers at the Norwegian Institute of Public Health and CRN have a long tradition of using these data sources to address research questions of common interests such as e.g. the effect of life style and diet on cancer risk. CRN and the Medical Birth Registry of Norway have co-existed for a long period, making it possible to study cancer incidence and birth characteristics over generations. During the last decades, several new registries such as the Norwegian Prescription Database and the Norwegian Patient Registry have been established, providing opportunities for studying for example drug use and cancer risk and the influence of comorbidities on the development of cancer. In the futu...
Cancer incidence, mortality, survival and prevalence in Norway
Because we have an aging population, the number of cancer cases increases every year. A total of 32 827 new cancer cases were diagnosed and reported in 2016. The changes are small compared with the previous year. In addition, we know that for most cancers there are some fluctuations in the rates from one year to another. Thus, to understand changes in the trends we need to compare the rates, not only from one year to another, but from the latest five-year period (2012)(2013)(2014)(2015)(2016) to the previous one (2007)(2008)(2009)(2010)(2011). This comparison shows a particularly large increase for melanoma of the skin, with more than a 20% increase since the previous five-year period among both men and women. Thyroid cancer is another cancer where we see a remarkable increase in incidence over time. Compared to the previous five-year period, there is a 30% rise in women, and more than 40% in men. This increase may be mostly due to increased use of ultrasound, computed tomography (CT) or magnetic resonance imaging (MRI) for other indications, and better cytological and/or histological diagnostics. We hope there is no opportunistic screening ongoing.
Acta Oncologica, 2006
The aim of the present study was to relate the time trends in breast cancer incidence and mortality to the introduction of mammography screening in the Nordic capitals. Helsinki offered screening to women aged 50 Á59 starting in 1986. The other three capitals offered screening to women aged 50 Á69 starting in 1989 in Stockholm, 1991 in Copenhagen, and 1996 in Oslo. Prevalence peaks in breast cancer incidence depended on the age groups covered by the screening, the length of the implementation of screening, and the extent of background opportunistic screening. No mortality reduction following the introduction of screening was visible after seven to 12 years of screening in any of the three capitals where significant effects of the screening on the breast cancer mortality had already been demonstrated by using other analytical methods for the evaluation. No visible effect on mortality reduction was expected in Oslo due to too short an observation period. The study showed that the population-based breast cancer mortality trend is too crude a measure to detect the effect of screening on breast cancer mortality during the first years after the start of a programme.