The stated conclusion of Archie Bleyer’s article, “Screening Mammography,” is “until we have better screening procedures that identify who really has cancer and needs to be treated, the risk of overdiagnosis relative to the benefit of screening merits more effective public and professional education.” Thus, my brief professional education to Dr. Bleyer and the public is as follows.
First, overdiagnosis of invasive breast cancer is a specious concept—superficially plausible, but actually wrong. Overdiagnosis is defined as diagnosis by screening of a cancer that never would have arisen symptomatically in the person’s lifetime, or never would have been detected if screening had not taken place. However, no one has a crystal ball to predict what will be the cause of a person’s death, spontaneous regression of an invasive cancer has never been reported, invasive cancer leads to metastasis, and metastatic cancer is associated with a low probability of survival. Therefore, the best medicine remains finding and treating invasive breast cancers so more women do not die from them.
Second, given that tumor size at the time of diagnosis is a well-established predictor of breast cancer mortality, the U.S. Department of Health and Human Services has established goals for screening mammography, including that >50% of screen-detected cancer should be stage 1 or 0 ductal carcinoma in situ (DCIS) . So yes, DCIS is found at higher numbers now by screening than it was in the prescreening era; yes, it is a legitimate concern how to appropriately manage DCIS; and yes, the answer is still unresolved. One day, it should be possible to accurately distinguish an aggressive from an indolent in situ breast cancer. However, in that hopefully not-too-distant future, we will still need to make the diagnosis . In other words, currently, there is not overdiagnosis, but rather possibly overtreatment in some cases.
Third, routine screening mammography reduces deaths from breast cancer by at least 20%–35%, as evidenced by a summary of every randomized controlled trial ever performed and data from the National Institutes of Health’s National Cancer Institute . In conclusion, if women do not get screened because of the fear of overdiagnosis, then the real risk will be of underdiagnosis , which is potentially fatal.
References
1. U.S. Department of Health and Human Services : Agency for healthcare research and quality (AHRQ). Quality determinants of mammography.1994. 82–85
2. Marmot M.G., Altman D.G., Cameron D.A., et. al.: The benefits and harms of breast cancer screening: an independent review. Lancet 2012; 380: pp. 1778-1786.
3. (SEER) NCIsSeaerp : SEER cancer statistics review 1975–2011. Available at http://seer.cancer.gov/csr/1975_2012/