Interval breast cancers in screening: The effect of mammography review method on classification

Abstract

Surveillance of interval cancers (IC) lacks standardisation of review methodologies. We investigated the extent to which 'informed' or 'blinded' review may affect IC classification. This is a retrospective study of 100 validated screening mammograms (20 IC, 80 negative screens) independently reviewed by six radiologists. Three sequenced review methods with increasing information were used: (1) blinded (no IC information, case mix), (2) partially informed, and (3) fully informed. IC 'screening error' (SE) reports averaged 24% (10-40), 33% (20-55), and 42% (35-50) for phases 1, 2, and 3, while 'minimal signs' (MS) reports averaged 6% (5-15), 10% (10-20), and 20% (15-30), respectively. Negative mammograms classification was MS in 18% (7-39) or SE in 19% (11-29), respectively. MS or SE classification was more likely for method 2 (OR=1.78, p=0.033) and method 3 (OR=3.91, p=0.000) relative to method 1, but no reader effect was evident. Inter-observer agreement in classifying at method 1 was slight (k 0.20), lowest (k 0.06) for MS, and fair (k 0.25) for negative and SE categories. More 'informed' review is more likely to yield an IC classification as MS or SE. Due to expected variability, review methods need standardisation to improve screening quality. Our data support blinded review of IC in mammography screening.

Phenotypic characterization and risk factors for interval breast cancers in a population-based breast cancer screening program in Barcelona, Spain

“…In addition, radiological classification of interval cancers is not easy to perform, and well-established protocols are lacking. Consequently, comparison of the results on interval cancers is difficult, given that many studies follow different strategies of interval classification [37]. We performed two mammographic reviews with both blinded and unblinded components, as recommended by the European Guidelines [4].…”

Analysis of interval cancers observed in an Italian mammography screening programme (2000–2006)

“…IC cases (N=100) and controls (N=200) did not differ as [8,9]. Il tasso di incidenza proporzionale e di ES così ottenuto sono stati confrontati con gli standard internazionali e con i risultati di altri programmi di screening nazionali e esteri.…”

“…IC review was largely within recommended values (SE rate=15% vs. ≤20% recommended) and confirmed a good performance of the Verona screening programme in terms of sensitivity. Blind review of IC is the most correct methodology to assess potential reading errors [8,9], as it tends to reproduce the current screening scenario, where radiologists are not aware of which cases will develop IC, among a large majority of true negative cases. Blind review, recommended by the Italian Study Group for Mammography Screening (GISMa) [1], has been recently suggested as a standard procedure by the Italian Ministry of Health [2].…”

“…Blind review is more respectful of screening radiologists compared with semiinformed review (only ICs are reviewed) or fully informed review (only ICs are reviewed, with the diagnostic mammogram available; that is, with information on IC side, site and features). Controlled studies have shown that blind review is associated with a lower proportion of reviewed cases being classified as SE [8,9].…”

Proportional incidence and radiological review of large (T2+) breast cancers as surrogate indicators of screening programme performance

“…A strength of the review strategy used in this work is the blinded classification and the case-mix (cancers and controls) which are recommended methods for radiological reviews to help reduce the bias in the classification of mammograms [7,11] and to approximate the scenario of screening practice [1,2]. Nonetheless, in a research context, reviewers might be expected to achieve higher sensitivity and lower specificity by adopting a lower threshold for suspicion, as suggested by the recall rates (see Table 2) which were higher than in routine practice, but comparable to other studies using radiological reviews [11][12][13]. The applied comparison of reviews of T2+ and ICs is reliable (performed by the same radiologist panel in the same setting using a standardised set of negative controls) and was performed to interrogate the extent to which preceding mammograms for these cancers would be classified as screening errors.…”