Screening for Breast Cancer Correlates with Significant Overdiagnosis

Overdiagnosis can result in no clinical benefit for patients, a study found.
Overdiagnosis can result in no clinical benefit for patients, a study found.

Screening for breast cancer correlated with significant overdiagnosis of the disease and did not correlate with a reduction in advanced tumors. Screening was also associated with increases in the discovery of nonadvanced tumors and ductal carcinoma in situ (DCIS).1

Ideally, screening for breast cancer detects early-stage disease and prevents advanced disease. Overdiagnosis can happen when mammography reveals small tumors that are unlikely to affect a patient's health during that patient's lifetime.

“Effective breast cancer screening should detect early-stage cancer and prevent advanced disease,” wrote the authors. Overdiagnosis can result in no clinical benefit while exposing the patient to the risks of treatment.

This study used data from 2 Danish cancer registries. Researchers investigated the correlation of screening with a reduced incidence of advanced cancer. They estimated the frequency of overdiagnosis in Denmark's breast cancer screening program. The program offers biennial mammography for women aged 50 to 69 years.

Researchers assessed the rate of advanced and nonadvanced tumors in both screened and unscreened women. To do this, they compared rates of advanced tumors in women between ages 50 years and 84 years in screening and nonscreening areas. They compared this to the incidence of nonadvanced tumors in women aged 35 to 49 years, 50 to 69 years, and 70 to 84 years in screening and nonscreening regions.

“Regional differences complicate interpretation,” the authors noted.

Screening was not associated with lower rates of advanced tumors. Additionally, approximately 1 in 3 invasive tumors and cases of ductal carcinoma in situ in screened women were cases of overdiagnosis.

These results support the mounting evidence that screening for breast cancer can result in overdiagnosis. Future research could address how to optimally use screening so as to avoid overdiagnosis.

Reference

1. Jørgensen KJ, Gøtzsche PC, Kalager M, Zahl PH. Breast cancer screening in Denmark: a cohort study of tumor size and overdiagnosis. Ann Intern Med. 2017 Jan 10. doi: 10.7326/M16-0270. [epub ahead of print]

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