| dc.description.abstract | Background: It has been suggested that the Norwegian National Breast Cancer Screening Program (NBCSP) should start to screen younger age groups. However, the current literature is in conflict, and there are no widely accepted estimate on both increased survival rates, and overdiagnosis as a result of screening. Objective: What is the minimum breast cancer mortality reduction amongst women aged 40-49 the Norwegian NBCSP needs to achieve, which makes extending the eligible participant population from age 50-69 to 40-69 considered cost-effective? Method: A Cost-Utility Analysis (CUA) was performed, where a reallocation of breast cancer patients to earlier stages simulated the present of screening. The reallocation of breast cancer patients were continued up to the point in which the Incremental Cost Effectiveness Ratio (ICER), was lower than the willingness-to-pay (WTP) per Quality Adjusted Life Year (QALY) gained threshold of kr 750 000. The risk reduction was then recorded. Multiple uncertainty analysis were conducted to analyze the impact of overdiagnosis. Result: With 15 % overdiagnosed patients, approximately 26.8% (relative) and 7.3% (absolute) risk reduction was needed if screening from age 40 was to be considered cost-effective. The estimated minimum risk reductions were highly dependent on the frequency of overdiagnosed patients. Conclusion: Based on the results, with 15% overdiagnosed patients, approximately 26.8% (relative) and 7.3% (absolute) risk reductions were needed for screening to be considered cost-effective. However, there are great uncertainty concerning the estimate, due to overdiagnosis. Additional knowledge of markers to identify tumors aggressiveness, could both reduce the uncertainty regarding overdiagnosis and cost-effectiveness, as well as reduce the impact of the main limitation of this thesis. Further research on tumor aggressiveness, is therefore recommended. | eng |