It was not until 1963 that the first RCT and the only RCT conducted within the United States commenced at the Health Insurance Plan of New York, Women were aged 40 to 64 at entry; nearly 62,000women were randomized to the study (two-view mammography and CBE) or control group (usual care). Two-view mammography and CBE) or ontrol group (usual care). Two-view mammography and physical examination were offered every 12 months for 3 years, and follow-up was continued for 18 years.
The Swedish Two-country Trial in Kopparberg and Ostergotland began in 1977 to 1978; 135,000 women were randomized to one-view mammography every 24 (younger than age 50 years) or 33 months (older than age 50 years). Within those geographic areas, all women were invited to enroll by letters of invitation, using the population registry list. Screening continued for four rounds for younger women and there rounds for older women.
The Malmo Trial was begun in 1976 in one city in Sweden. It was one of only two trials that began screening at age 45 years, and it sopped entry at age 69 years. It used tow-view mammography every 18 to 24 months for five rounds; randomization was by cluster based on birth cohort. Approximately 68,000 women were enrolled in this trial.
The Stockholm Study began in 1981 and enrolled approximately 59,000 women aged 40 to 49 years was by individual, whereas clustered randomization was used for women aged 50 to 59 years, who received tow-view mammography every 18 months. Randomization of women aged 40 to 49 years was by individual, whereas clustered randomization was used for women aged 50 to 59 years. Verified results have not yet been published, but additional data were provided in 1997 for the Nationa Institutes of Health Consensus Conference on Breast Cancer Screening in women aged 40 to 49 years.
The Edinburgh trial began in 1976 as a randomized component of the larger, nonrandomized United Kingdom trial for the Early Detection of Breast Cancer. Approximately 45,000 women aged 45 to 64 years were randomized to two-view mammography plus CBE on either a 12 or 24 month schedule. The purpose was to assess the impact of mammography and CBE in reducing mortality from breast cancer.
The NBSSI was designed to examine the value of two-view mammography and CBE compared to usual care in women aged 40 to 49. Approximately 50,000 women were enrolled, starting in 1980, and received follow-up yearly for 5 years. Unlike the other trials, the women were recruited as volunteers and then randomized. As miller et al have reported, these women were different from the rest of the Canadian population in several ways – for example, they were less likely to smoke, and they had higher levels of education.
The second Canadian study, the NBSS2, also begun in 1980, enrolled nearly 40,000 women aged 50 to 59 years, and was designed to compare two-view mammography and CBE against CBE only. In other words, the question was whether mammography has benefits over and above CBE in this age group. This is the only trial planned to assess the additive impact of mammography in addition to CBE. Critiques of this trial have appeared by several authors. The criticisms are probably overstated, and the results should be discounted.
Non Randomized Clinical trials
A number of nonrandomized trials have been conducted around the world. Much can be learned from these studies. However, because of a number of design limitations, their results alone should not be used in establishing screening guidelines and policies. The largest study of mammography and CBE was the US. Breast Cancer Detection Demonstration Project (BCDDP): 280,000 women aged 35 and older were recruited and screened in 28 centers annually with mammograms and CBE during the 1970s. The BCDDP was sponsored jointly by the NCI and the ACS. Because BCDDP participants were not a random sample of the population, there were some important differences from women in the general population. Most notably, the BCDDP population was at much higher risk, with a substantially higher incidence of breast cancer. Subsets of women were followed as part of a case-control study conducted by Morrison et al. to examine case fatality rates within the BCDDP. Breast cancer mortality was approximately 20% less than expected from national data. A benefit was seen for younger women, but it was less than for older women.
The Swedish Two-country Trial in Kopparberg and Ostergotland began in 1977 to 1978; 135,000 women were randomized to one-view mammography every 24 (younger than age 50 years) or 33 months (older than age 50 years). Within those geographic areas, all women were invited to enroll by letters of invitation, using the population registry list. Screening continued for four rounds for younger women and there rounds for older women.
The Malmo Trial was begun in 1976 in one city in Sweden. It was one of only two trials that began screening at age 45 years, and it sopped entry at age 69 years. It used tow-view mammography every 18 to 24 months for five rounds; randomization was by cluster based on birth cohort. Approximately 68,000 women were enrolled in this trial.
The Stockholm Study began in 1981 and enrolled approximately 59,000 women aged 40 to 49 years was by individual, whereas clustered randomization was used for women aged 50 to 59 years, who received tow-view mammography every 18 months. Randomization of women aged 40 to 49 years was by individual, whereas clustered randomization was used for women aged 50 to 59 years. Verified results have not yet been published, but additional data were provided in 1997 for the Nationa Institutes of Health Consensus Conference on Breast Cancer Screening in women aged 40 to 49 years.
The Edinburgh trial began in 1976 as a randomized component of the larger, nonrandomized United Kingdom trial for the Early Detection of Breast Cancer. Approximately 45,000 women aged 45 to 64 years were randomized to two-view mammography plus CBE on either a 12 or 24 month schedule. The purpose was to assess the impact of mammography and CBE in reducing mortality from breast cancer.
The NBSSI was designed to examine the value of two-view mammography and CBE compared to usual care in women aged 40 to 49. Approximately 50,000 women were enrolled, starting in 1980, and received follow-up yearly for 5 years. Unlike the other trials, the women were recruited as volunteers and then randomized. As miller et al have reported, these women were different from the rest of the Canadian population in several ways – for example, they were less likely to smoke, and they had higher levels of education.
The second Canadian study, the NBSS2, also begun in 1980, enrolled nearly 40,000 women aged 50 to 59 years, and was designed to compare two-view mammography and CBE against CBE only. In other words, the question was whether mammography has benefits over and above CBE in this age group. This is the only trial planned to assess the additive impact of mammography in addition to CBE. Critiques of this trial have appeared by several authors. The criticisms are probably overstated, and the results should be discounted.
Non Randomized Clinical trials
A number of nonrandomized trials have been conducted around the world. Much can be learned from these studies. However, because of a number of design limitations, their results alone should not be used in establishing screening guidelines and policies. The largest study of mammography and CBE was the US. Breast Cancer Detection Demonstration Project (BCDDP): 280,000 women aged 35 and older were recruited and screened in 28 centers annually with mammograms and CBE during the 1970s. The BCDDP was sponsored jointly by the NCI and the ACS. Because BCDDP participants were not a random sample of the population, there were some important differences from women in the general population. Most notably, the BCDDP population was at much higher risk, with a substantially higher incidence of breast cancer. Subsets of women were followed as part of a case-control study conducted by Morrison et al. to examine case fatality rates within the BCDDP. Breast cancer mortality was approximately 20% less than expected from national data. A benefit was seen for younger women, but it was less than for older women.
