Effect of Screening Mammography on Breast Cancer Incidence

Abstract

To the Editor: As Bleyer and Welch report (Nov. 22 issue),¹ screening mammography has had a limited effect on breast cancer mortality in the United States; over the course of 30 years, age-adjusted incidence rates of late-stage cancers have decreased by only 8%, and no significant change is noticeable in the incidence rates of cancers diagnosed after they have metastasized to distant organs. Similar studies in the United Kingdom, the Netherlands, Italy, Switzerland, Norway, and Australia have shown limited decreases, if any, in the incidence of advanced breast cancers after 15 to 20 years of widespread screening.²–⁴ Hence, it . . .

To the Editor: As Bleyer and Welch report (Nov. 22 issue),¹ screening mammography has had a limited effect on breast cancer mortality in the United States; over the course of 30 years, age-adjusted incidence rates of late-stage cancers have decreased by only 8%, and no significant change is noticeable in the incidence rates of cancers diagnosed after they have metastasized to distant organs. Similar studies in the United Kingdom, the Netherlands, Italy, Switzerland, Norway, and Australia have shown limited decreases, if any, in the incidence of advanced breast cancers after 15 to 20 years of widespread screening.²–⁴ Hence, it seems that everywhere it has been introduced, the effectiveness of screening mammography has been marginal. However, randomized trials of screening mammography have also reported reductions in the risk of death from breast cancer that were directly correlated with reductions in the risk of receiving a diagnosis of advanced breast cancer.⁵ It is therefore important to understand why such a discrepancy in results exists between randomized mammography trials and general population screening. One hypothesis deserving further investigation is that in trials, factors other than screening mammography may have contributed to the reduction in the numbers of women receiving a diagnosis of advanced breast cancer.

No potential conflict of interest relevant to this letter was reported.