Neglected aspects of false positive findings of mammography in breast cancer screening: analysis of false positive cases from the Stockholm trial

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Abstract
Objectives: To examine the implications of false positive results of mammography in terms of the time lag from screening and complete mammography to the point when women with false positive results are declared free of cancer; the extra examinations, biopsies, and check ups required; and the cost of these extra procedures. Design: Review of women with false positive results from the Stockholm mammography screening trial. Setting: Department of Oncology, South Hospital, Stockholm. Subjects: 352 and 150 women with false positive results of mammography from the first and second screening rounds of the Stockholm trial. Main outcome measures: Extra examinations and investigations required and the cost of these procedures. Results: The 352 women from the first screening round made 1112 visits to the physician and had 397 fine needle aspiration biopsies, 187 mammograms, and 90 surgical biopsies before being declared free of cancer. After six months 64% of the women (219/342) were declared cancer free. The 150 women in the second round made 427 visits to the physician and had 145 fine needle aspiration biopsies, 70 mammograms, and 28 surgical biopsies, and after six months 73% (107/147) were declared cancer free. The follow up costs of the false positive screening results were Kr2.54m (pounds sterling250000) in the first round and Kr0.85m (pounds sterling84000) in the second round. Women under 50 accounted for about 41% of these costs. Conclusions: The examinations and investigations carried out after false positive mammography—especially in women under 50—and the cost of these procedures are a neglected but substantial problem. Key messages These extra costs come from the examinations and investigations required during follow up—for example, repeated biopsy of benign tissue—before the patient is declared cancer free In this series the costs of following up women with false positive mammograms were almost one third of the cost of screening all women in the randomised Stockholm mammography trial These extra costs and other negative aspects of false positive results of mammography—especially in women under 50—are a neglected but substantial problem The benefits of mammography must be carefully weighed against the potential negative aspects, especially in women under 50