UK Study Suggests Association Between Screen-Detected Ductal Carcinoma in Situ and Reduced Invasive Interval Breast Cancers
In a UK retrospective population-based study reported in The Lancet Oncology, Duffy et al found a significant inverse association between the detection of ductal carcinoma in situ in breast cancer screening and the incidence of invasive interval cancers diagnosed within 3 years after screening. However, estimates indicated that higher ductal carcinoma in situ detection rates were associated with diminishing returns in terms of invasive interval cancers avoided.
Study Details
The study involved data from 84 local screening units in 11 regional centers in England, Wales, and Northern Ireland, where mammography screening is offered every 3 years. Data on ductal carcinoma in situ diagnoses were obtained for 5,243,658 women aged 50 to 64 years who underwent screening between April 2003 and March 2007 (4 screening years). Patient-level data for interval cancers in the 36 months after each of the screening years were analyzed by Poisson regression.
Key Results
The average frequency of screen-detected ductal carcinoma in situ was 1.60 per 1,000 women screened. The rate of screen-detected ductal carcinoma in situ was inversely associated with the rate of invasive interval cancers (Poisson regression coefficient = –0.084, P = .002). It was estimated that for screen-detected ductal carcinoma in situ rates up to approximately 1.5/1,000 women, 1 interval invasive cancer was avoided for every 2 screen-detected ductal carcinoma in situ cases; for screening-detected ductal carcinoma in situ rates > 1.5/1,000 women, it was estimated that 1 invasive cancer was avoided for every 6 ductal carcinoma in situ cases.
A total of 90% of screening units had a ductal carcinoma in situ detection rate in the range of 1.00 to 2.22/1,000 women; in these units, for every 3 cases of ductal carcinoma in situ, there was 1 less invasive interval cancer. Analyses adjusting for small screen-detected invasive cancers and grade 3 invasive screen-detected cancers yielded similar results.
The investigators concluded: “The association between screen-detected ductal carcinoma in situ and subsequent invasive interval cancers suggests that detection and treatment of ductal carcinoma in situ is worthwhile in prevention of future invasive disease.”
The study was funded by the UK Department of Health Policy Research Programme and the National Health Service Cancer Screening Programmes.
Stephen W. Duffy, MSc, of Queen Mary University of London, is the corresponding author of The Lancet Oncology article.
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