Abstract
SummaryBackgroundThe value of screen detection and treatment of ductal carcinoma in situ (DCIS) is a matter of controversy. At present, the extent to which the diagnosis and treatment of DCIS could prevent the occurrence of invasive breast cancer in the future is not clear. We sought to estimate the association between detection of DCIS at screening and invasive interval cancers subsequent to the relevant screen.MethodsWe obtained aggregate data for screen-detected cancers from 84 local screening units within 11 regional Quality Assurance Reference Centres in England, Wales, and Northern Ireland from the National Health Service Breast Screening Programme. Data for DCIS diagnoses were obtained for women aged 50–64 years who were invited to and attended mammographic breast screening from April 1, 2003, to March 31, 2007 (4 screening years). Patient-level data for interval cancer arising in the 36 months after each of these were analysed by Poisson regression with invasive interval cancer screen detection rate as the outcome variable; DCIS detection frequencies were fitted first as a continuous and then as a categorical variable. We repeated this analysis after adjustment with both small size and high-grade invasive screen-detected cancers.FindingsWe analysed data for 5 243 658 women and on interval cancers occurring in the 36 months after the relevant screen. The average frequency of DCIS detected at screening was 1·60 per 1000 women screened (median 1·50 [unit range 1·54–3·56] per 1000 women). There was a significant negative association of screen-detected DCIS cases with the rate of invasive interval cancers (Poisson regression coefficient −0·084 [95% CI −0·13 to −0·03]; p=0·002). 90% of units had a DCIS detection frequency within the range of 1·00 to 2·22 per 1000 women; in these units, for every three screen-detected cases of DCIS, there was one fewer invasive interval cancer in the next 3 years. This association remained after adjustment for numbers of small screen-detected invasive cancers and for numbers of grade 3 invasive screen-detected cancers.InterpretationThe association between screen-detected DCIS and subsequent invasive interval cancers suggests that detection and treatment of DCIS is worthwhile in prevention of future invasive disease.FundingUK Department of Health Policy Research Programme and NHS Cancer Screening Programmes.
Highlights
ductal carcinoma in situ (DCIS) was rare in the era before screening, and a major question is the extent to which diagnosis and treatment of DCIS could prevent the occurrence of invasive breast cancer in the future.[4]
We searched PubMed with the search terms “ductal carcinoma in situ” and “screening” and “breast” and “invasive” and “incidence” for publications reporting on studies of any design investigating the effect of screen detection of DCIS on incidence of subsequent invasive cancer, published in any language between Jan 1, 1990, and July 31, 2015
Using data from the UK National Health Service Breast Screening Programme (NHSBSP) we identified a significant negative association between the number of DCIS cases detected at screening and the number of invasive cancers occurring in the subsequent 3-year interval
Summary
The benefit-to-harm balance of screen detection and subsequent treatment of ductal carcinoma in situ of the breast (DCIS) has been a matter of debate.[1,2,3] DCIS was rare in the era before screening, and a major question is the extent to which diagnosis and treatment of DCIS could prevent the occurrence of invasive breast cancer in the future.[4] In two randomised trials of screening, an excess of DCIS in the study groups was almost entirely balanced by a corresponding deficit in invasive disease.[5] Further, in a trial of treatment of DCIS, those cases who had only received wide local excision had a 10-year rate of subsequent breast cancer events of more than 30%, suggesting a serious potential of DCIS for progression.[6] The fact remains, that for any individual DCIS case that is treated, it cannot be known for certain what would have happened if the treatment had not taken place.[6] with sufficient aggregate data, it might be possible to assess the effect of screen detection of DCIS on the subsequent incidence of invasive cancer in a population subject to screening
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