Research Article

Use of Mastectomy for Overdiagnosed Breast Cancer in the United States: Analysis of the SEER 9 Cancer Registries

Figure 1

Main analysis of overtreatment by mastectomy in the study population, which consists of all women diagnosed with breast cancer at age ≥40 in 2013 in the SEER 9 cancer registries. The percentage of patients with breast cancer who undergo mastectomy for overdiagnosed cancer is unknown. However, our main analysis determines the range of possible values that are consistent with the known characteristics of breast cancer cases in the study population. Specifically, in the above figure, the x axis shows the percentage of the study population who were overdiagnosed, the y axis shows the percentage of the study population who underwent mastectomy for overdiagnosed cancer, and the shaded region shows the range of values that are consistent with the known characteristics of breast cancer cases. For example, if 20% of the study population was overdiagnosed then, based on the known characteristics of the breast cancer cases, we can conclude that somewhere between 1% and 11% of the study population received mastectomy for overdiagnosed cancer. As another example, if 0% of the study population was overdiagnosed, then 0% received mastectomy for overdiagnosed cancer. Additionally, if 37% was overdiagnosed, then somewhere between 5% and 18% received mastectomy for overdiagnosed cancer. (The figure shows a range of possible values for percentage overdiagnosed because there is little consensus regarding the true number, with potential values extending from near 0% to 37%.) The analysis includes both invasive and in situ breast cancers.