Mammography screening in the Netherlands: delay in the diagnosis of breast cancer after breast cancer screening

In a prospective study we determined the frequency and causes of delay in the diagnosis of breast cancer after suspicious screening mammography. We included all women aged 50-75 years who underwent biennial screening mammography in the southern breast cancer screening region of the Netherlands between 1 January 1996 and 1 January 2002. Clinical data, breast imaging reports, biopsy results and breast surgery reports were collected of all women with a positive screening result with a minimum of 2-year follow-up. Of 153 969 mammographic screening examinations, 1615 (1.05%) were positive screens. Breast cancer was diagnosed in 770 (47.9%) of 1607 women for whom follow-up information was available, yielding a cancer detection rate of 5.0 per 1000 women screened. Breast cancer was diagnosed within 3 months following a positive screen in 722 cases (93.8%). The diagnostic delay was 4-6, 7-12 and 13-24 months, respectively, in 11 (1.4%), 24 (3.1%) and nine (1.2%) patients. In four other patients (0.5%), breast cancer was diagnosed after a repeat positive screen, resulting in a diagnostic delay of 25-27 months. Reasons for a diagnostic delay >3 months were erroneous mammographic interpretation of suspicious lesions as benign or probably benign lesions (33 cases), benign biopsies from a malignant lesion (10), and omission to biopsy or remove a lesion that was suspicious at breast imaging (4) or core biopsy (1). We conclude that there is room for improvement in the workup of patients with a positive screening mammography, as seen from data in this screening region. To improve the workup, we suggest that other breast cancer screening programmes also identify delay in breast cancer diagnosis after a positive screen.