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- Tabar, L, et al.
(författare)
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Beyond randomized controlled trials - Organized mammographic screening substantially reduces breast carcinoma mortality
- 2001
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Ingår i: Cancer. - 0008-543X .- 1097-0142. ; 91:9, s. 1724-1731
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND, The efficacy of mammographic screening in the reduction of breast carcinoma mortality has been demonstrated in randomized controlled trials. However, the evaluation of organized screening outside of research settings (so-called "service screening") faces unique methodologic and conceptual challenges. The current study describes the evaluation of organized mammography screening in a clinical setting and demonstrates the benefit obtained from service screening in two Swedish counties. METHODS. In the group of subjects ages 20-69 years, there were 6807 women diagnosed with breast carcinoma over a 29-year period in 2 counties in Sweden and 1863 breast carcinoma deaths. All patients were classified from patient charts based on their screening status (i.e., whether they had been invited to undergo screening and whether they actually had undergone screening). The number of women who lived in the 2 counties during the 29-year study period was provided by the Central Bureau of Statistics. Breast carcinoma-specific mortality was compared across three time periods: 1) 1968-1977, when no screening was taking place because mammography had not been introduced, 2) 1978-1987, the approximate period of the Two-County randomized controlled trial of screening in women ages 40-74 years, and 3) 1988-1996, when all women in the 2 counties ages 40-69 years were invited to undergo screening (service screening). When comparing breast carcinoma mortality in screened women with that in women diagnosed before screening was introduced, a correction for self-selection bias was incorporated to prevent overestimation of the benefit of screening. RESULTS. The mortality from incident breast carcinoma diagnosed in women ages 40-69 years who actually were screened during the service screening period (1988-1996) declined significantly by 63% (relative risk [RR] = 0.37, 95% CI, 0.30-0.46) compared with breast carcinoma mortality during the time period when no screening was available (1968-1977). The mortality decline was 50% (RR = 0.50, 95% CI, 0.41-0.60) when breast carcinoma mortality among all women who were invited to undergo screening (nonattendees included) was compared with breast cancer mortality during the time period when no screening was available (1968-1977). The reduction in mortality observed during the service screening period, adjusted for selection bias, was 48% (RR = 0.52, 95% CI, 0.43-0.63). No significant change in breast carcinoma mortality was observed over the three time periods in women who did not undergo screening. This group included women ages 20-39 years because these individuals were never invited to undergo screening, and women ages 40-69 years who did not undergo screening (not invited during the randomized trial or invited during the second and third time periods but declined). CONCLUSIONS. Regular mammographic screening resulted in a 63% reduction in breast carcinoma death among women who actually underwent screening. The policy of invitation to organized screening with mammography appears to have reduced breast carcinoma mortality by 50% in these 2 counties. (C) 2001 American Cancer Society.
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| 3. |
- Wang, HG, et al.
(författare)
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Interval cancers in the Norwegian Breast Cancer Screening Program : Frequency, characteristics and use of HRT
- 2001
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Ingår i: International Journal of Cancer. - 0020-7136 .- 1097-0215. ; 94:4, s. 594-598
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Tidskriftsartikel (refereegranskat)abstract
- Breast cancers diagnosed between screening examinations among women who attend a breast cancer screening program are defined as interval cancers. The Norwegian Breast Cancer Screening Program started as a pilot project in 1996, and data from the first 2-year interval are available. Our study quantifies interval cancers in the pilot project and explores characteristics and factors that may be associated with interval cancer. Interval cancers in the screening population were identified through the Cancer Registry of Norway. The frequency of invasive interval cancer was calculated as cases per 10,000 screened and as observed/expected ratio. Characteristics of the interval cancers were compared to screening-detected and clinical cancers. Breast density was assessed in a blinded review of 3 categories of screening mammograms. Information on hormone replacement therapy (HRT) use was collected from a questionnaire. The frequency of invasive interval cancers was 18.2 (15.9-20.7) per 10,000 screened and the observed/expected ratio was 0.49 (0.43-0.56). The frequency in the second year of the interval was higher than reported from other programs. The median tumor size of the interval cancers was 19.5 mm and 44.0% of the patients had affected axillary lymph nodes. The interval cancer cases had higher proportions of dense breasts and reported use of HRT compared to screen normal and screening-detected cases. The reported frequency of interval cancers is similar to comparable programs. The interval cancers differed significantly from the cancers detected in the first screening round and were more similar to clinical cancers. Interval cancer was associated with dense breasts and use of HRT. Screening programs must keep these associations in focus. (C) 2001 Wiley-Liss, Inc.
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