Landmark Study

Impact of Mammography and Adjuvant Therapy on the Decline in U.S. Breast Cancer Mortality: 1975–2000.   

After remaining relatively constant for many years, breast cancer mortality in the United States decreased by a dramatic 24% from 1989 to 2000. CISNET investigators initiated a joint comparative modeling effort among seven groups to determine the contributions of mammography and adjuvant therapy to this decline. While the benefits of adjuvant therapy were more settled, controversy regarding the benefits of mammography screening persisted due to uneven results and continuing criticism of the controlled trials on which the mortality benefits had been based. The dissemination and usage patterns of mammography and adjuvant therapy were coupled with seven independent modelers' syntheses of all available information on the benefits of these advances to estimate their population impact.

Dissemination of Screening and Adjuvant Therapy

Changes in the pattern of screening mammography use among women Changes in the use of adjuvant therapy

Changes in the pattern of screening mammography use among women 40 to 79 years of age, and change in the use of adjuvant therapy among women 50 to 69 years of age with node positive stage II or IIIA breast cancer. Copyright © 2005 Massachusetts Medical Society. All rights reserved.

All models agree on three points:

  1. Both screening and treatment reduced breast cancer mortality,
  2. The observed reduction in the overall population could not be attributed to either one acting alone, and
  3. Each contributed about equally to this decline.

Typically, results based on observational data are validated using controlled trials. However, this was a case where observational data (combined in a novel way using seven different models) helped to confirm mammography benefits, when controlled trial results alone could not settle the debate.

Mortality Trends and Results of Joint Modeling Effort

Estimated and actual mortality rates from breast cancer among women 30 to 79 years of age Estimated joint distribution of the reduction in the rate of death from breast cancer

Left: Estimated and actual mortality rates from breast cancer among women 30 to 79 years of age under hypothetical assumption about the use of screening mammography and adjuvant treatment.

Right: Estimated joint distribution of the reduction in the rate of death from breast cancer among U.S. women 30 to 79 years of age that is attributable to adjuvant treatment and screening mammography. Letters represent point estimates from each of the seven CISNET models.
Copyright © 2005 Massachusetts Medical Society. All rights reserved.

This analysis was first published in the The New England Journal of Medicine:

Berry DA, Cronin KA, Plevritis SK, Fryback DG, Clarke L, Zelen M, Mandelblatt JS, Yakovlev AY, Habberna JDF, Feuer EJ. Effect of Screening and Adjuvant Therapy on Mortality from Breast Cancer. New Eng J Med 2005 Oct 27;353(17):12-20. [Abstract]

In addition, a JNCI monograph describes the details of each of the seven models, the common inputs, and the results. The monograph provides the opportunity to examine the links between results and the model structures to give insight into the complex relationship between modeling assumptions and conclusions, exemplifying the benefits obtained from a comparative modeling approach.

Cancer Intervention and Surveillance Modeling Network (CISNET) Breast Cancer Collaborators. The Impact of Mammography and Adjuvant Therapy on U.S. Breast Cancer Mortality (1975-2000): Collective Results from the Cancer Intervention and Surveillance Modeling Network. J Natl Cancer Inst Monographs 2006;36:1-126. [Monograph]