Elsevier

The Lancet Oncology

Volume 7, Issue 3, March 2006, Pages 259-265
The Lancet Oncology

Review
Radiological surveillance of interval breast cancers in screening programmes

https://doi.org/10.1016/S1470-2045(06)70617-9Get rights and content

Summary

Interval breast cancers—those diagnosed after a negative mammographic screen and before the next scheduled screen—are an important indicator of the potential effectiveness of population screening for breast cancer. Although the incidence of interval cancers is usually monitored, radiological surveillance is not undertaken routinely in most screening programmes. Here, we describe radiological surveillance of interval breast cancers and discuss methodological difficulties in the radiological review process and in the categorisation of interval cancers as false-negative, true, or occult. Furthermore, we identify methods that affect whether an interval cancer is classified as a false-negative (missed) or a true interval cancer. For all radiological categories of interval cancers, we outline possible changes to screening programmes that might improve cancer detection. Standardised radiological surveillance of interval cancers might allow within-programme comparisons and has the potential to guide practice and improve quality.

Introduction

Population screening for breast cancer is widely undertaken in health-care systems of industrialised countries, and most organised breast screening programmes (figure 1) monitor the occurrence of interval cancers—ie, those diagnosed after a negative mammographic screen and before the next scheduled screen. However, radiological surveillance (continuing mammographic review and classification) of interval breast cancers is not routine practice in most breast screening programmes, outside of evaluation studies. Here, we define radiological surveillance of interval breast cancers and identify methodological difficulties in the radiological review process and in categorisation of intervals as false-negative, true, or occult. Furthermore, we outline how information from radiological surveillance can guide potential screening methods and research aimed at control of interval breast cancers in screening.

Section snippets

Epidemiological surveillance

Early detection by mammographic screening reduces breast cancer mortality in randomised trials.1 The benefit from breast screening is largely dependent on the quality of the screening programme, and a low rate of interval cancers is an important indicator of the success of cancer screening in practice.2, 3, 4 Cancer screening programmes thus monitor the incidence of interval cancers as an indicator of screening effectiveness. This observation forms part of epidemiological surveillance, with

Definition of interval cancers and radiological surveillance

An interval breast cancer is diagnosed after a (negative) mammographic screen and before the next scheduled screen—ie, in the interscreening interval. This definition includes cancers not identified at the time of screening (most interval cancers) and those recalled because of a positive screen but (incorrectly) dismissed after assessment; this group of recalled cancers forms a small proportion of all interval cancers.4 The definition does not include cancers detected at routine screening that

False-negative interval cancers

These cancers are present on the screening mammogram but are not recognised by the radiologist (or film reader) at the time of screening. They might be perception errors, in which the abnormality is present on the film but is not seen by the film reader, or interpretation errors, in which the abnormality is seen by the film reader but is interpreted as not being malignant disease. False-negative interval cancers can be further classified into two types: abnormalities that are regarded as

Conclusion

Radiological review of interval breast cancers as part of quality improvement in screening is not universally used in organised breast screening programmes, or it can be restricted to evaluation studies or isolated case-review. Radiological surveillance of interval breast cancers is a broader and more continuous process than radiological review, and it has the potential to guide public-health decisions about changes to screening programmes. Radiological surveillance means that valid,

Search strategy and selection criteria

We identified relevant published work with a MEDLINE search, using the following strategy: we exploded the MeSH term “breast neoplasms” (from 1966 to April, 2005) and searched the term “interval cancer”. Abstracts were read by one author (NH) and full papers were reviewed if they provided information on any aspect of radiological review of interval breast cancers. Additional papers were identified through the reference list of relevant papers and by discussion with content experts.

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