Effect of screening mammography on breast-cancer mortality in Norway

Area of Science:

• Oncology
• Public Health
• Epidemiology

Background:

• Quantifying the impact of screening mammography on breast-cancer mortality presents challenges in establishing valid comparison groups.
• Historical control groups may not accurately reflect current trends due to advancements in breast-cancer treatment and awareness.

Purpose of the Study:

• To evaluate the effectiveness of screening mammography in reducing breast-cancer mortality.
• To differentiate the impact of screening mammography from other factors influencing mortality rates.

Main Methods:

• The Norwegian breast-cancer screening program data from 1996-2005 was analyzed.
• Incidence-based mortality rates were compared between screening and non-screening counties, using historical comparison groups from 1986-1995.
• Data from 40,075 women diagnosed with breast cancer were analyzed.

Main Results:

• A reduction in breast-cancer death rates was observed in both screening and non-screening groups compared to their historical counterparts.
• Screening mammography was associated with a 7.2 deaths per 100,000 person-years reduction in the screening group and 4.8 deaths per 100,000 person-years in the non-screening group.
• Screening mammography alone accounted for approximately one-third of the total observed reduction in breast-cancer mortality.

Conclusions:

• Screening mammography is associated with a decrease in breast-cancer mortality rates.
• The study highlights that screening mammography is not the sole factor contributing to reduced mortality; other factors play a significant role.
• The findings underscore the importance of considering multiple factors when assessing the impact of screening programs.