Canadian National Breast Screening Study

Canadian National Breast Screening Study

The Canadian National Breast Screening Study (CNBSS) was a randomized controlled trial designed to evaluate the effectiveness of breast cancer screening in reducing mortality. Initiated in 1980 and concluding its initial phase in 1985, the study enrolled 89,835 women aged 40 to 59 across Canada. It aimed to assess the impact of mammography and physical examination of the breasts in detecting breast cancer early and improving survival rates.

Background

Breast cancer is a leading cause of death among women worldwide. Early detection through screening is believed to reduce mortality rates. The CNBSS was developed in response to growing demand for scientific evidence supporting the effectiveness of breast cancer screening programs.

Methodology

Participants were randomly assigned to two groups: the screening group, which received annual mammography and physical examinations, and the control group, which received only usual care without specific screening. The study's primary endpoint was breast cancer mortality.

Findings

The CNBSS published its results in several phases, with key findings indicating that there was no significant difference in breast cancer mortality between the screened group and the control group after a follow-up period of up to 25 years. These results sparked significant debate within the medical community regarding the benefits of routine mammographic screening.

Controversies

The CNBSS faced criticism for various aspects of its methodology, including the randomization process, the quality of mammography, and the handling of screen-detected lesions. Critics argued that these factors might have influenced the study's findings.

Impact

Despite the controversies, the CNBSS has had a significant impact on breast cancer screening policies and practices. It has contributed to the ongoing debate about the age at which screening should start and the frequency of screening. The study's long-term follow-up continues to provide valuable data for understanding the complexities of breast cancer screening.

See Also

• Breast cancer screening
• Mammography
• Randomized controlled trial
• Cancer epidemiology

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