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

Retrospective radiological review and classification of interval breast cancers within population-based breast screening programmes for the purposes of open disclosure: A systematic review

INTRODUCTION

Interval breast cancers occur following a negative breast screening mammogram and before the next scheduled appointment within screening programmes. Radiological review classifies them as cancers that develop between screens, cancers with no obvious malignant abnormalities on prior screens or cancers not detected at screening. This study aimed to systematically review published literature on the occurrence of open disclosure following interval cancer radiological reviews by breast screening programmes internationally in a retrospective setting and examine methodologies used for radiological reviews for the purposes of disclosure.

METHODS

A search for relevant articles published (January 2000 - May 2019) was conducted according to PICO and PRISMA guidelines. The databases Pubmed, Scopus, Google Scholar, Cinahl, Web of Science, Embase, Science Direct and Global Health were searched. Relevant studies were reviewed if they had completed a retrospective review and classification of interval breast cancers.

RESULTS

Of 46 relevant articles included, no study was identified that conducted a retrospective review purposely for open disclosure. Retrospective reviews were conducted for audit/quality assurance, and research including for radiologist education and learning. Variation in methodology was found across review type (non-blinded/semi-informed approach), number of reviewers and classification categories. The proportion of false negative cancers classified among the studies ranged from 4 to 40 %.

DISCUSSION

Variation among radiological review practices were observed, which likely impacts classification results. To ensure standardised classification of interval breast cancers are employed for the purposes of open disclosure in screening settings, reproducible and consistent methodology is required.

Interval Cancers in Breast Cancer Screening: Comparison of Stage and Biological Characteristics with Screen-Detected Cancers or Incident Cancers in the Absence of Screening

Aims and background

To analyze stage distribution and biological features of interval cancers observed in Verona mammography screening compared to screen-detected cancers and “clinical” cancers occurring in the absence of screening, as provided by the Veneto Cancer Registry.

Methods and study design

Screen-detected cancers were identified in the screening archives. Interval cancers and clinical cancers (occurring in women never screened or not yet invited) were identified through the local cancer registry. Studied variables were age, stage, pathological pT and pN category, histological grading, estrogen and progesterone receptor status, and proliferation index (Ki67).

Results

We compared 95 interval cancers, 761 screen-detected cancers, and 1873 clinical cancer cases. Interval cancers had more aggressive features than screen-detected cancers, the difference being statistically significant for pT (P = 10–6), pN (P = 0.0003), grading (P = 0.007), estrogen receptors (P = 0.0006), and progesterone receptors (P = 0.00005), but not for Ki67 (P = 0.18). The features of interval cancers were not more aggressive than those of clinical cancers for pT (P = 0.84), pN (P = 0.33), grading (P = 0.61), estrogen receptors (P = 0.48), and progesterone receptors (P = 0.69), and were better for Ki67 (P = 0.02). In contrast, screen-detected cancers showed significantly better features than clinical cancers, for all studied variables: pT (P = 10–6), pN (P = 10–6), grading (P = 10–6), estrogen receptors (P = 10–5), progesterone receptors (P = 10–6), and Ki67 (P = 10–6).

Conclusions

Our findings are consistent with the length biased sampling hypothesis of interval cancers having a faster growth rate and a less favorable presentation than screen-detected cancers. Compared to clinical cancers, interval cancers had similar features, whereas screen-detected cancers had definitely more favorable features. This finding suggests, rather than a faster growth rate for interval cancers, a slower growth rate for screen-detected cancers, which, together with diagnostic anticipation, may explain a certain degree of overdiagnosis.

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

An interval breast cancer is a cancer that emerges following a negative mammographic screen. This overview describes the epidemiology, and the radiological and biological characteristics of interval breast cancers in population mammography screening. Notwithstanding possible differences in ascertainment of interval breast cancers, there was broad variability in reported interval breast cancer rates (range 7.0 to 49.3 per 10,000 screens) reflecting heterogeneity in underlying breast cancer rates, screening rounds (initial or repeat screens), and the length and phase of the inter-screening interval. The majority of studies (based on biennial screening) reported interval breast cancer rates in the range of 8.4 to 21.1 per 10,000 screens spanning the two-year interval with the larger proportion occurring in the second year. Despite methodological limitations inherent in radiological surveillance (retrospective mammographic review) of interval breast cancers, this form of surveillance consistently reveals that the majority of interval cancers represent either true interval or occult cancers that were not visible on the index mammographic screen; approximately 20–25% of interval breast cancers are classified as having been missed (false-negatives). The biological characteristics of interval breast cancers show that they have relatively worse tumour prognostic characteristics and biomarker profile, and also survival outcomes, than screen-detected breast cancers; however, they have similar characteristics and prognosis as breast cancers occurring in non-screened women. There was limited evidence on the effect on interval breast cancer frequency and outcomes following transition from film to digital mammography screening.

Characterisation of microcalcification clusters on 2D digital mammography (FFDM) and digital breast tomosynthesis (DBT): does DBT underestimate microcalcification clusters? Results of a multicentre study

OBJECTIVES

To compare DBT and FFDM in the classification of microcalcification clusters (MCs) using BI-RADS.

METHODS

This Institutional Review Board-approved study was undertaken in three centres. A total of 107 MCs evaluated with both DBT and FFDM were randomised for prospective reading by six experienced breast radiologists and classified using BI-RADS.

RESULTS

The benign/malignant ratio of MC was 66/41. Of 11/107 discordant results, DBT classified MCs as R2 whereas FFDM classified them as R3 in 9 and R4 in 2. Three of these (3/107 = 2.8%) were malignant; 8 (7.5%) were nonmalignant and were correctly classified as R2 on DBT but incorrectly classified as R3 on FFDM. Estimated sensitivity and specificity, respectively, were 100% (95% CI: 91% to 100%) and 94.6% (95% CI: 86.7% to 98.5%) for FFDM and 91.1% (95% CI: 78.8% to 97.5%) and 100% (95% CI: 94.8% to 100%) for DBT. Overall intra- and interobserver agreements were 0.75 (95% CI: 0.61-0.84) and 0.73 (95% CI: 0.62-0.78).

CONCLUSIONS

Most MCs are scored similarly on FFDM and DBT. Although a minority (11/107) of MCs are classified differently on FFDM (benign MC classified as R3) and DBT (malignant MC classified as R2), this may have clinical relevance.

KEY POINTS

• The BI-RADS classification of MC differs for FFDM and DBT in 11/107 cases • DBT assigned lower BI-RADS classes compared to FFDM in 11 clusters • In 4/107 DBT may have missed some malignant and high-risk lesions • In 7/107 the 'underclassification' on DBT was correct, potentially avoiding unnecessary biopsies • DBT may miss a small proportion of malignant lesions.

Incremental effect from integrating 3D-mammography (tomosynthesis) with 2D-mammography: Increased breast cancer detection evident for screening centres in a population-based trial

BACKGROUND & OBJECTIVES

Three-dimensional (3D)-mammography (tomosynthesis) may improve breast cancer detection. We examined centre-specific effect of integrated 2D/3D mammography based on the STORM (screening with tomosynthesis or standard mammography) trial.

METHODS

Asymptomatic women who attended population-based screening through Trento and Verona screening centres were recruited into STORM, a prospective comparison of screen-reading in two sequential phases: 2D-mammography only and integrated 2D/3D mammography. Outcomes were the number and rates of detected cancers and of false positive recalls (FPR), and incremental cancer detection rate (CDR). Paired binary data were compared using Mc Nemar's test.

RESULTS

Of 33 cancers detected in Trento, 21 were detected at both 2D and 2D/3D screening, 12 cancers were detected only with integrated 2D/3D screening compared with none detected at 2D-only screening (P < 0.001). Of the 26 cancers detected in Verona, 18 were detected at both 2D and 2D/3D screening, 8 cancers were detected only with integrated 2D/3D screening compared with none detected at 2D-only screening (P = 0.008). There were no differences between centres in baseline CDR, and incremental CDR attributable to 3D-mammography was similar for Trento (2.8/1000 screens) and for Verona (2.6/1000 screens). Trento had 239 FPR (5.7% of screens): 103 FPR at both screen-readings, 93 FPR only at 2D-mammography compared with 43 FPR only at 2D/3D-mammography (p < 0.001). Verona had 156 FPR (5.2% of screens): 78 FPR at both screen-readings, 48 FPR only at 2D-mammography compared with 30 FPR only at 2D/3D-mammography (p = 0.054). Estimated reduction in FPR proportion had recall been conditional to 2D/3D-mammography-positivity differed between centres (21.0% versus 11.5%; P = 0.02).

CONCLUSION

Integrated 2D/3D-mammography significantly increased cancer detection for both screening services; potential reduction in FPR is likely to differ between centres with those experiencing relatively higher FPR most likely to benefit from 2D/3D-mammography screening.

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

PURPOSE

To evaluate the performance of the first years since the beginning of a mammographic population-based screening program.

MATERIALS AND METHODS

Women aged 49-69 were invited biennially for two-view film-screen mammography and double reading without arbitration was performed. Interval cancers (ICs) from 2001 to 2006 were identified using screening archives, local pathology archives, and hospital discharge records. The proportional incidence of IC was determined considering breast cancers expected without screening. Three offsite radiologists experienced in breast cancer screening blindly evaluated mammograms prior to diagnosis, randomly mixed with negative mammograms (1:2 ratio). Cases unrecalled at review were considered as true ICs, those recalled by only one reviewer as minimal signs, and those recalled by two or three reviewers as missed cancers. T and N stage of the reviewed ICs were evaluated and compared.

RESULTS

A total of 86,276 first level mammograms were performed. Mean recall rate was 6.8% at first and 4.6% at repeat screening. We had 476 screen-detected cancers and 145 ICs (10 of them ductal carcinomas in situ). Absolute incidence was 17 per 10,000 screening examinations. Invasive proportional incidence was 19% (44/234) in the first year, 39% (91/234) in the second year, and 29% (135/468) in the two-year interval. Of 145 ICs, 130 (90%) were reviewed mixed with 287 negative controls: 55% (71/130) resulted to be true ICs, 24% (31/130) minimal signs, and 22% (28/130) missed cancers. The rate of ICs diagnosed in the first year interval was 21% (15/71) for true ICs, 46% (13/28) for missed cancers, and 39% (12/31) for minimal signs, with a significant difference of true ICs rate compared to missed cancers rate (p=0.012). A higher rate of T3 and T4 stages was found for missed cancers (18%, 5/28) compared to minimal signs (6%, 2/31) or true ICs (8%, 6/71), while the rate of N2 and N3 stage for both minimal signs (19%, 6/31) or missed cancers (25%, 7/28) was higher than that for true ICs (10%, 7/71), although all these differences were not significant (p ≥ 0.480).

CONCLUSION

These results showed the possibility to comply with European Community standards in the first years of a screening program implementation.

Integration of 3D digital mammography with tomosynthesis for population breast-cancer screening (STORM): a prospective comparison study

BACKGROUND

Digital breast tomosynthesis with 3D images might overcome some of the limitations of conventional 2D mammography for detection of breast cancer. We investigated the effect of integrated 2D and 3D mammography in population breast-cancer screening.

METHODS

Screening with Tomosynthesis OR standard Mammography (STORM) was a prospective comparative study. We recruited asymptomatic women aged 48 years or older who attended population-based breast-cancer screening through the Trento and Verona screening services (Italy) from August, 2011, to June, 2012. We did screen-reading in two sequential phases-2D only and integrated 2D and 3D mammography-yielding paired data for each screen. Standard double-reading by breast radiologists determined whether to recall the participant based on positive mammography at either screen read. Outcomes were measured from final assessment or excision histology. Primary outcome measures were the number of detected cancers, the number of detected cancers per 1000 screens, the number and proportion of false positive recalls, and incremental cancer detection attributable to integrated 2D and 3D mammography. We compared paired binary data with McNemar's test.

FINDINGS

7292 women were screened (median age 58 years [IQR 54-63]). We detected 59 breast cancers (including 52 invasive cancers) in 57 women. Both 2D and integrated 2D and 3D screening detected 39 cancers. We detected 20 cancers with integrated 2D and 3D only versus none with 2D screening only (p<0.0001). Cancer detection rates were 5.3 cancers per 1000 screens (95% CI 3.8-7.3) for 2D only, and 8.1 cancers per 1000 screens (6.2-10.4) for integrated 2D and 3D screening. The incremental cancer detection rate attributable to integrated 2D and 3D mammography was 2.7 cancers per 1000 screens (1.7-4.2). 395 screens (5.5%; 95% CI 5.0-6.0) resulted in false positive recalls: 181 at both screen reads, and 141 with 2D only versus 73 with integrated 2D and 3D screening (p<0.0001). We estimated that conditional recall (positive integrated 2D and 3D mammography as a condition to recall) could have reduced false positive recalls by 17.2% (95% CI 13.6-21.3) without missing any of the cancers detected in the study population.

INTERPRETATION

Integrated 2D and 3D mammography improves breast-cancer detection and has the potential to reduce false positive recalls. Randomised controlled trials are needed to compare integrated 2D and 3D mammography with 2D mammography for breast cancer screening.

FUNDING

National Breast Cancer Foundation, Australia; National Health and Medical Research Council, Australia; Hologic, USA; Technologic, Italy.

Interobserver agreement in breast radiological density attribution according to BI-RADS quantitative classification

PURPOSE

The authors sought to assess interobserver agreement in classifying mammography density according to quantitative Breast Imaging Reporting and Data System (BI-RADS) criteria.

MATERIALS AND METHODS

Six expert mammography readers were tested on a set of 100 mammograms. Interobserver agreement was determined according to the kappa statistic, adjusting for chance agreement, on a four-category (D1 vs. D2 vs. D3 vs. D4) or two-category (D1-2 vs. D3-4) basis. Agreement with a panel of 12 readers who had been tested on the same set in a previous study was also assessed.

RESULTS

The six readers showed good agreement when compared in pairs [agreement on a four-category basis was substantial (kappa=0.60-0.80) for 13 pairs and almost perfect (kappa>0.80) for two pairs); agreement on a two-category basis was substantial for 12 pairs and almost perfect for three pairs) or compared with the panel (on a four-category basis, agreement was substantial for five of six readers and almost perfect for one; on a two-category basis, agreement was substantial for all readers).

CONCLUSIONS

In agreement with previous studies, visual classification of mammography density according to BI-RADS quantitative criteria was highly reproducible among readers; nevertheless, attribution to the "dense breast" (BI-RADS D3-4) category, which might be adopted as a determinant of different screening protocols (such as adjunct ultrasonography or yearly interval) varied among readers (range 6-15%). Controlled studies should be performed comparing visual with computer-density category attribution, the latter possibly being a better alternative due to its absolute reproducibility.

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

OBJECTIVES

Surrogate measures of screening performance [e.g. interval cancer (IC) proportional incidence] allow timely monitoring of sensitivity and quality. This study explored measures using large (T2+) breast cancers as potential indicators of screening performance.

METHODS

The proportional incidence of T2+ cancers (observed/expected cases) in a population-based screening programme (Trento, 2001-2009) was estimated. A parallel review of 'negative' preceding mammograms for screen-detected T2+ and for all ICs, using 'blinded' independent readings and case-mixes (54 T2+, 50 ICs, 170 controls) was also performed.

RESULTS

T2+ cancers were observed in 168 screening participants: 48 at first screen, 67 at repeat screening and 53 ICs. The T2+ estimated proportional incidence was 68% (observed/expected = 168/247), corresponding to an estimated 32% reduction in the rate of T2+ cancers in screening participants relative to that expected without screening. Majority review classified 27.8% (15/54) of T2+ and 28% (14/50) of ICs as screening error (P = 0.84), with variable recall rates amongst radiologists (8.8-15.2%).

CONCLUSIONS

T2+ review could be integrated as part of quality monitoring and potentially prove more feasible than IC review for some screening services.

KEY POINTS

• Interval breast cancers, assumed as screening failures, are monitored to estimate screening performance • Large (T2+) cancers at screening may also represent failed prior screening detection • Analysis of T2+ lesions may be more feasible than assessing interval cancers • Analysis of T2+ cancers is a potential further measure of screening performance.

Evidence of interval cancer proportional incidence and review from mammography screening programs in Italy

Purpose

To summarize the existing evidence on the proportional incidence and review of interval cancers, as reported by Italian screening programs.

Material and methods

Literature search of published reports on: a) proportional incidence, determined according to breast cancers expected in the absnce of screening and estimated on the basis of patients/year at risk and age-specific incidence; and b) review of screening mammograms preceding interval cancers. Results were compared with European Commission recommended standards.

Results

Evidence on proportional incidence or review of interval cancers was reported by 37 and 24 local health unit programs, respectively. Compared to European Commission standards, 94% and 87% of programs complied at first interval cancers survey with recommended standards for proportional incidence or screening error rate at review, respectively. Two programs initially below acceptable standards reached satisfactory results at repeat evaluation over time.

Conclusions

Although they are a minority (20%) of all local health unit programs, which suggests a possible selection bias, Italian surveys reporting data on the proportional incidence or review of interval cancers show an overall good performance. Interval cancer survey appears feasible in any program and should become a routine procedure within the national quality control system.

Benefits of double reading of screening mammograms: retrospective study on a consecutive series

PURPOSE

The purpose of this study was to assess the performance of delayed second reading of screening mammograms when added to real-time reading plus immediate assessment.

MATERIAL AND METHODS

The study setting was the mammography screening programme of an Italian Local Health Unit. Recall rate and cancer detection rate at first reading or informed second reading only were assessed in a cohort of 23,629 women aged 50-69 years screened during 2007-2008. Incremental recall rate, incremental cancer detection rate and incremental cost of second reading were determined.

RESULTS

Recall rate was 13.0% at first and 2.7% at second reading (incremental recall rate +21.1%). Overall, recalls were more frequent in the younger decade and in the presence of denser breasts. Cancer detection rate was 7.06‰ (n=167) at first and 0.93‰ (n=22) at second reading (incremental cancer detection rate +13.1%). Compared with first reading, second reading detected more cancers depicted as isolated microcalcifications and distortions (40.9% vs. 16.2%, p=0.02) and at a lower stage (stage 0-I 81.8% vs. 69.5%, p=0.34). The cost of adding delayed second reading was + <euro> 3.65 per screened individual or <euro> 3,926.61 per incremental cancer detected.

CONCLUSIONS

The study confirms the efficacy of second reading, even as an adjunct to real-time single reading plus immediate assessment. Incremental recall rate is acceptable in view of the incremental cancer detection rate, and both figures are within the range of literature reports on double-reading performance.