Purpose: Ductal carcinoma in situ (DCIS), a nonobligate precursor to invasive breast cancer, makes up 20% of new breast cancer diagnoses. DCIS is primarily detected by mammography and has excellent prognosis regardless of therapy choice. We aim to quantify the impact of detection and treatment of DCIS on breast cancer mortality using computer modeling.

Methods: We used a validated microsimulation model to replicate U.S. trends in breast cancer incidence and mortality from 1975 to 2000. All breast cancer tumors began in the in situ stage and progressed through more advanced stages with increasing tumor size and lymph node involvement, with a fraction of tumors assumed as nonlethal. Age-adjusted breast cancer mortality was examined under historical U.S. screening and treatment patterns and three alternative scenarios: (1) only women 50 years and older received screening and all breast cancer cases received treatment according to historical patterns, (2) all women received screening according to historical patterns but DCIS was untreated unless later detected at an invasive stage, and (3) historical screening was used but DCIS was never treated.

Results: The model predicts breast cancer mortality rates declined during the 1990s to a low of 39.9 per 100,000 in 2000, which is consistent with observed mortality based on the SEER program (38.0 per 100,000 in 2000). Delaying mammography until age 50 or postponing treatment until DCIS progressed to invasive cancer increased mortality to 42.4 and 43.2 per 100,000, respectively, by 2000. If DCIS patients did not receive any treatment, mortality remained steady (∼51.2 per 100,000) through 2000.

Conclusions: Our model results suggested detection and treatment of DCIS in the U.S. reduced breast cancer deaths in the year 2000 by about 28%. Most of this benefit (92%–94%) could also be achieved if instead mammography began at age 50 or treatment was reserved for invasive breast cancers only.

This abstract is one of the 14 highest scoring abstracts of those submitted for presentation at the 35th Annual Meeting of the American Society of Preventive Oncology, held March 5–8, 2011 in Las Vegas, NV.