No abstract

In March 1981, 40,318 women in Stockholm, aged 40-64, entered a randomized trial of breast cancer screening by single-view mammography alone versus no intervention in a control group of 20,000 women. The attendance rate during the first screening round was 81 per cent and the cancer detection rate was 4.0 per 1000 women. The detection the rate fell to 3.1 per 1000 in the second round, which was completed in October 1985. During 1986 the controlled design of the study was broken and the control women were invited once to screening which was completed the same year. A total of 428 cases of breast cancer were thus diagnosed in the study group and 439 in the adjusted control group. After a mean follow-up of 7.4 years the number of breast cancer deaths in the study and control groups was 39 and 30 respectively. The relative risk of breast cancer death (screening versus control) was 0.71 (95 per cent confidence interval: 0.4-1.2). Among women older than 50 years at entry the relative risk was 0.57 (95 percent confidence interval: 0.3-1.1). Cancer deaths among women under 50 were few and perhaps because of this no mortality reduction was seen in this age group. The estimate of mortality reduction lies between the results from two earlier Swedish randomized controlled trials.

In March 1981 a randomized single-view mammographic screening for breast cancer was started in the south of Stockholm. The screened population in the first round numbered 40,318 women, and 20,000 women served as a well-defined control group. The age groups represented were 40-64 years, and 80.7% of the invited women participated in the study. The first round disclosed 128 breast cancers (113 invasive and 15 noninvasive), or 4.0 per 1,000 women. Mean tumour size was 14.1 mm and axillary lymph node metastases were found in 21.8%. Fifty-five per cent of the tumours were small (less than or equal to 10 mm) or non-invasive, and 71% were stage I. Participation rates are high in all Swedish trials. The present results differ only slightly from other screening programs; the percentages of patients with axillary metastases and stage II tumours are similar in the Stockholm, Malmö and Kopparberg/Ostergötland studies. Comparisons of cancer prevalence in the various Swedish screening trials show that, in comparable age groups, there are some differences, even when the differences in the natural cancer incidence are taken into account. A decreased mortality was found recently in a Swedish trial in ages above 50 years but not below. In the Stockholm study more than one-third of the participants were aged 40-49 years.

Prophylactic treatment with the anti-estrogen tamoxifen may reduce the risk of breast cancer because estrogens are thought to act as promoters in the pathogenesis of the disease. This article presents results on the incidence of contralateral new primary tumors among 1846 postmenopausal breast cancer patients included in a randomized trial of adjuvant tamoxifen therapy for 2 or 5 years after surgery versus no adjuvant endocrine therapy. The median follow-up was 7 years (range, 3-13 years). There was a significant reduction of contralateral breast cancer in the 931 patients in the tamoxifen group versus that in the 915 control patients (29 versus 47 cases, respectively; P = .03). The cumulative incidence at 10 years in the tamoxifen group and the control group was 5% and 8%, respectively. Analysis of the relative hazard of contralateral tumor over time showed that the benefit with tamoxifen therapy was greatest during the first 1-2 years, but there was a continued risk reduction during the entire follow-up period, i.e., more than 10 years after cessation of treatment. There was no significant difference in the number of contralateral cancers in the patients randomly assigned to 2 or 5 years of treatment, but the 95% confidence interval of the relative hazard was wide. The proportion of estrogen receptor-negative contralateral breast cancers was higher in the tamoxifen group than in the control group. There was no difference, however, between the two groups in recurrence-free survival time from the diagnosis of the contralateral cancer.(ABSTRACT TRUNCATED AT 250 WORDS)