Abstract P2-04-02: Increased Risk of Breast Cancer in Women Who Receive False Positive Test Results from Mammography Screening

Abstract

Abstract Background: Copenhagen has the longest running organised screening programme for breast cancer in Denmark. The programme started in 1991. One of the possible consequences when screening for breast cancer with mammography is a false positive test result. We assessed the relative risk of developing breast cancer among women who had received false positive test results compared to women who had not. Method: The mammography programme provided data on participation and test results from 1991 -2005. Oncological data was retrieved from the National Cancer Register. Follow-up ended on 17 April 2008. Data were linked using the Danish unique personal identity number. Relative risks were estimated using Poisson regression, age adjusted. The exposure was categorised as a) false-positive Type1 = negative after further assessment with mammography, ultrasound and fine needle aspiration, and b) Type 2 = negative after surgery. Results: A total of 59.392 women participated in the mammography programme, representing 650.218 person-years at risk. The relative risk (RR) of breast cancer after any type of false positive (FP) was 1.33 (95% CI, 1.18-1.50), the RR for breast cancer after a Type 1 FP was 1.34 (95% CI, 1.18 — 1.52) and after a Type 2 FP the RR was 1.24 (95% CI, 0.85-1.82). The RR of interval cancer, i.e. breast cancer within the two years following the test result, was 1.73 (95% CI, 1.13-2.66) for women who had received a FP test result as compared to those who had not. Conclusion: Women who have received a false positive test result from mammography screening had a 73% increased risk of developing interval cancer compared to women who had not, and a 33% increased risk of developing breast cancer at any time after a false positive test result. There was an increased risk for both Type 1 (34%) and Type 2 (24%) FP test results, though data was only significant for Type 1 results. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-04-02.