Interval breast cancers: Absolute and proportional incidence and blinded review in a community mammographic screening program

The epidemiology, radiology and biological characteristics of interval breast cancers in population mammography screening

“…4, 13, 15–29 The table highlights the broad variability in both interval BC rates and cancer detection rates at screening, both of which are partly driven by underlying cancer rates in the populations reported in these studies. There is wide variability in the overall interval BC rates, ranging between 7.0 and 49.3 per 10,000 screens, partly explained by data shown for screening rounds (initial and repeat screens) and the duration and year of the inter-screening intervals; where reported, data for the inter-screening interval are presented by yearly rates for biennial or triennial screening.…”

“…1 Table 2 summarises findings from the literature search on radiological surveillance including the methods used to conduct mammographic review; 10, 13–15, 18, 26, 31–40 the latter substantially influences the distribution of radiological categories and can bias estimated proportions. 1, 33, 41 For example, a pilot study examining radiological review methods showed that informed vs. blinded (uninformed) review of interval BC leads to bias in classification whereby informed reviewers (aware they were reviewing mammograms containing interval cases) more frequently classified some interval BCs as positive, compared to reviewers who were unaware they were reading mammograms of interval BCs that had been added into routine screen-reading practice (‘uniformed’ review).…”

“…Radiological surveillance entails review of the mammograms taken at the time the interval BC is identified (usually at clinical presentation, hence the diagnostic mammograms) and the pre-diagnosis mammographic screen (the ‘negative’ index screen) and an interpretative judgement to classify each case into pre-defined categories. 1, 13–15 These categories may vary in definition, however, most include a ‘true interval’ category (where the cancer is not visible at the index screen but becomes visible at the diagnostic mammogram) and a ‘missed’ interval BC being the equivalent of a false-negative (where the cancer is visible on the index mammogram but is not recalled or is misinterpreted) and is at times referred to as screening error. 1, 13–15 Various methods have been used to perform radiological surveillance, as described in a review by Houssami et al 1 with potential biases inherent in the review strategy and the extent that readers are informed that they are evaluating interval BC cases.…”

“…1, 13–15 These categories may vary in definition, however, most include a ‘true interval’ category (where the cancer is not visible at the index screen but becomes visible at the diagnostic mammogram) and a ‘missed’ interval BC being the equivalent of a false-negative (where the cancer is visible on the index mammogram but is not recalled or is misinterpreted) and is at times referred to as screening error. 1, 13–15 Various methods have been used to perform radiological surveillance, as described in a review by Houssami et al 1 with potential biases inherent in the review strategy and the extent that readers are informed that they are evaluating interval BC cases. 1 Notwithstanding the methodological limitations of radiological surveillance, it provides insights into screening quality and on how screening could be improved.…”

Mammography: an update of the EUSOBI recommendations on information for women

“…This rule also applies to mammography. When thinking about screening, women should be aware that about 28 % of cancers can be missed [13, 14], especially in pre-menopausal women and in those with dense breasts. This means that if we consider 1000 women getting a screening mammogram, if 8–10 cancers are present, 2 or 3 can be missed, mostly because they are difficult to distinguish from normal breast tissue.…”