It is not clear whether screening for breast cancer works as public health policy and whether early indicators of effect predict an ultimate reduction in mortality. The malignant potentials of 248 breast cancers detected by the screening service in Finland were compared with those of 490 control cancers diagnosed before the screening service was established. Aggressiveness was assessed by DNA flow cytometry and clinical status by cancer size and node involvement. After the first screening round, the results of DNA flow cytometry were the same in cancers diagnosed by screening and in controls; these findings are consistent with the hypothesis that the biological aggressiveness of breast cancer remains constant as the cancer progresses. The proportion of patients with node-negative and small T1 cancers after the first screening was higher among the screened population than among controls, indicating earliness of diagnosis among those screened. Cancers diagnosed in the first round had a low malignant potential, as indicated by the DNA flow-cytometry and by clinical stage. Lower aggressiveness of cancers found by screening than of control cancers would indicate overdiagnosis or length-biased sampling, but not earliness of diagnosis. Screening with mammography is practised as a public-health policy in Finland. The results predict that the mortality reduction found in randomised trials can be repeated with a screening service.
A nationwide mammographic screening for breast cancer was started in Finland in 1987. During the first 2 years of the organised screening programme, 126,000 women were invited. Most of them (103,000) belonged to the birth year cohort in the 50-59 years' age groups. Among the 112,000 screenees, 418 cancers (0.4%) were found. Specificity of the test was about 96%. The screening prevalence was 2.4 times the annual incidence and a minimum estimate for the detection rate among those invited was 1.6 times that among those not invited. These estimates indicate a relatively low test and programme sensitivity. The final effectiveness of a public health policy cannot be predicted on the basis of limited preventive trials, and there is need to evaluate also a public health policy by experimental means.
Cites: Lancet. 1984 Jun 2;1(8388):1222-46144933
Cites: Lancet. 1984 Jun 2;1(8388):1224-66144934
Cites: Lancet. 1985 Apr 13;1(8433):829-322858707
Cites: Br J Cancer. 1985 Oct;52(4):669-734063143
Cites: Lancet. 1990 Feb 3;335(8684):241-61967717
Cites: Int J Cancer. 1988 Nov 15;42(5):697-7023182106
A prospective study was conducted to investigate the possible effect of breast self-examination (BSE) on cause-of-death-specific survival rate of breast cancer patients. Six hundred and four breast cancer patients diagnosed in 1984-1986 in Finland, and applying for breast prostheses, were interviewed about both their BSE practices prior to cancer diagnosis and the actual method of tumor detection. No clear differences were observed in the stage distribution or cause of death-specific five-year survival rates between individuals with different BSE practices. After adjustment for potential confounders in the Cox proportional hazards analysis, no differences in risk of breast cancer death were observed for those who performed BSE monthly as compared to those who practised BSE less frequently or not at all. When the method of detection was taken into account, it turned out that only 34 (7.6 %) of the 448 regular BSE practisers had actually detected their cancers by means of BSE. Furthermore, no survival advantage was associated with detection of breast cancer by means of BSE. Those BSE practisers whose cancer was detected by BSE had a similar or slightly worse prognosis compared to BSE practisers whose cancer had been detected by other means. Our results suggest that BSE practice is not beneficial in terms of breast cancer survival, nor is detection of breast cancer by means of BSE. Conclusive evidence should, however, be obtained from prospective randomized studies of breast cancer mortality.
BACKGROUND - Screening for ovarian cancer is based on ultrasound, colour Doppler, and tumour markers. There is only limited evidence on their discriminatory performance and no evidence on their effectiveness in reducing mortality. OBJECTIVE - To investigate the discriminatory performance of CA 125 as a screening test for ovarian cancer. METHODS - A registry of 15 093 serum samples drawn in 1968-72 was linked to the cancer registry. During follow up between 1968 and 1980 24 ovarian cancers were identified. One or two matched case-control design nested within the sample bank was applied and the concentrations of CA 125 were assessed. RESULTS - Case-control differences (relative risk 4-0, 95% confidence interval 1.0 to 15.5 at 20 kU/1) were found. Detection rate of the CA 125 test was 21-33% and the true negative rate was 75-98% depending on the cut off level and interval between drawing of the blood sample and diagnosis of the cancer. CONCLUSION - CA 125 is not a valid screening test if used alone. Case-control differences of borderline significance were found in CA 125 before diagnosis of ovarian cancer, but they were not large enough to provide a sufficient detection rate.
Long term trends in the incidence of and mortality from invasive cervical cancer have been studied in Finland (1953-1987) and Estonia (1968-1987). The analyses are based on the data from the Finnish and Estonian Cancer Registries. An organised nationwide screening programme for cervical cancer was started in Finland in the early 1960s. In Estonia, no cytological screening programme has been introduced, and cervical malignancies are diagnosed in routine gynaecological practice. During 1968-1987, both the incidence of and mortality from cervical cancer were considerably higher in Estonia than in Finland. A decrease has taken place in the cervical cancer incidence and mortality in both countries since the mid-1960s, but whereas in Finland the decrease has been marked, in Estonia it has been less pronounced and levelled off in the 1980s. In 1987, the age-standardised (world population) incidence rate per 100,000 women was 14.0 in Estonia and 3.8 in Finland, and the age-standardised mortality rate was 6.0 and 1.6 per 100,000, respectively. The difference in the incidence of the disease in the two neighbouring countries can be partially attributed to socioeconomic factors. The main reason for the different slopes of the trend curves for cervical cancer is probably the difference in public health policies: an effective mass screening programme is being conducted in Finland but not in Estonia.
The basis for primary prevention of cancer is well-established, because significant causes of cancer are known. However, apart from reducing cigarette smoking, few easily applicable measures to decrease cancer incidence are available. Recently, there has been much interest in chemoprevention in cancer control, with several international bodies, including the International Union Against Cancer (UICC) and the European Union (EU), making important contributions. The results and relevance of these studies are discussed. Many of the problems associated with evaluating cancer prevention strategies generally apply particularly to chemoprevention, and these issues also are addressed.
To evaluate the effectiveness of screening for breast cancer as a public health policy.
Follow up in 1987-92 of Finnish women invited to join the screening programme in 1987-9 and of the control women (balanced by age and matched by municipality of residence), who were not invited to the service screening.
Of the Finnish women born in 1927-39, 89893 women invited for screening and 68862 controls were followed; 1584 breast cancers were diagnosed.
Rate ratio of deaths from breast cancer among the women invited for screening to deaths among those not invited.
There were 385 deaths from breast cancer, of which 127 were among the 1584 incident cases in 1987-92. The rate ratio of death was 0.76 (95% confidence interval 0.53 to 1.09). The effect was larger and significant (0.56; 0.33 to 0.95) among women aged under 56 years at entry. 20 cancers were prevented (one death prevented per 10000 screens).
A breast screening programme can achieve a similar effect on mortality as achieved by the trials for breast cancer screening. However, it may be difficult to justify a screening programme as a public health policy on the basis of the mortality reduction only. Whether to run a screening programme as a public health policy also depends on its effects on the quality of life of the target population and what the resources would be used for if screening was not done. Given all the different dimensions in the effect, mammography based breast screening is probably justifiable as a public health policy.
In Finland, the organized mass screening program for the early detection of cervical cancer covers, with few exceptions, all women between the ages of 30 and 55 every fifth year. On the basis of material originating from the Finnish Cancer Registry it was estimated that the probability for a woman aged 30-59 to experience frankly invasive cervical cancer was 0.010 before the screening program, and 0.002 after the first screening. The corresponding probability estimate was 0.022 for pre-invasive lesions subjected to operative treatment. On the assumption that the same relationship applies beyond this age group it was estimated that from 28-39% of the pre-invasive cases progress to invasive cervical cancer, and that 21% of the frankly invasive cases are preceded by a pre-invasive stage of shorter duration than the time period between the screenings, or have no preclinical stage.