Breast‐cancer mortality in a non‐randomized trial on mammographic screening in women over age 65

Abstract

Recent case-referent studies in the Nijmegen breastscreening programme have shown a reduction in breastcancer mortality of approximately 50% due to screening of women aged 65 years and older. In this type of study, however, the results may be biased because of self-selection. The purpose of our present study was to compare the breast-cancer mortality rate in a population invited for screening with that of a reference population from an area without a screening programme. In 1977-1978, 6773 women aged 68-83 years were enrolled in the mammographic screening programme in Nijmegen, The Netherlands. The women were followed up until 31 December, 1990. The reference population consisted of women from the same birth cohort from Arnhem, a neighbouring city without mass screening, for whom the entry date was 1 January, 1978. The ratios of the Nijmegen and Arnhem breast-cancer mortality rates with 95% confidence intervals (CI) were calculated. In the study period, 173 patients were diagnosed with primary breast cancer in Nijmegen vs. 183 in Arnhem; 40 Nijmegen patients had died of breast cancer vs. 51 Arnhem patients. The cumulative mortality-rate ratio was 0.80 (95% CI 5 0.53-1.22). In the periods 1978-1981, 1982-1985 and 1986-1990, the mortality rate ratios were 1.44 (95% CI 5 0.67-3.10), 0.81 (95% CI 5 0.37-1.79) and 0.53 (95% CI 5 0.27-1.04), respectively. After adjustment for the difference in incidence rate that existed between the Nijmegen and Arnhem populations, mammographic screening of women older than 65 can be expected to yield a 40% reduction in breast-cancer mortality after 10 years. Int. J. Cancer, 70:164-168, 1997.r 1997 Wiley-Liss, Inc.Unlike most malignancies, the course of breast cancer can be altered by early detection and treatment. In women over the age of 50 years, trials have shown a reduction of breast-cancer mortality of some 25 to 30% in populations that were offered screening vs. unscreened populations (Fletcher et al., 1993; Nyström et al., 1993;De Koning et al., 1995;Kerlikowske et al., 1995). The screening intervals used in these studies ranged from 12 to 33 months and the screening test consisted of 1-or 2-view mammography, sometimes in combination with physical examination.More recently, a reduction in mortality has been demonstrated in women up to the age of 75 years (Van Dijck et al., 1994Chen et al., 1995). The results of the Swedish 2-county study, which was a randomized trial, showed a decrease in breast-cancer mortality due to the screening of women aged 65 to 74 years at entry (Chen et al., 1995). After 14 years of follow-up, a statistically significant 32% reduction in the risk of death from breast cancer was observed in the population invited for screening. In Nijmegen, 2 case-referent studies included women aged 65 years and older at the index invitation (i.e., the most recent invitation to screening just prior to the diagnosis of breast cancer in the case). The estimated reductions in breast-cancer mortality in women screened at the index invitation relative to those unscreened a...

Stage and treatment variation with age in postmenopausal women with breast cancer: compliance with guidelines

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Tailored messages, external barriers, and women's utilization of professional breast cancer screening over time

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Service screening mammography reduces breast cancer mortality among elderly women in Turku

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