Readers of your Nov. 22 article “Mammogram effectiveness questioned; Study finds treatment for nonlife-threatening breast cancers” should be aware that the research article you cite provides a seriously flawed examination of the impact of widespread breast cancer screening.
The authors of the study claim that screening mammograms find too many low-grade cancers that will not progress or threaten the life of patients if they are left untreated. They base this claim on an incorrect assumption that the rate of occurrence of breast cancer is much higher than would have been expected had screening not been introduced.
The authors compound their error by intentionally including in their data cases of Ductal Carcinoma in Situ, or DCIS.
DCIS is an early, noninvasive form of breast cancer that mammograms are particularly well suited to detect.
By pooling DCIS cases with invasive cancers, the authors are stacking the deck unfairly to bolster their claim that screening studies lead to overdiagnosis and treatment of nonlife-threatening disease.
If one corrects for that bias, there is no overdiagnosis of invasive breast cancer.
The media are quick to report papers that question the value of screening mammography.
Articles that refute these poorly designed studies often are not reported.
It would be a great shame if women, understandably confused by conflicting claims caused by shoddy research, were to opt out of screening studies that could save their lives.
DR. ROBIN SHERMIS
Editor’s note: The writer is director of breast imaging at ProMedica Breast Care.
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