Screening-detected breast cancers: discordant independent double reading in a population-based screening program

Discordant and false-negative interpretations at digital breast tomosynthesis in the prospective Oslo Tomosynthesis Screening Trial (OTST) using independent double reading

OBJECTIVES

To analyze discordant and false-negatives of double reading digital breast tomosynthesis (DBT) versus digital mammography (DM) including reading times in the Oslo Tomosynthesis Screening Trial (OTST), and reclassify these in a retrospective reader study as missed, minimal sign, or true-negatives.

METHODS

The prospective OTST comparing double reading DBT vs. DM had paired design with four parallel arms: DM, DM + computer aided detection, DBT + DM, and DBT + synthetic mammography. Eight radiologists interpreted images in batches using a 5-point scale. Reading time was automatically recorded. A retrospective reader study including four radiologists classified screen-detected cancers with at least one false-negative score and screening examinations of interval cancers as negative, non-specific minimal sign, significant minimal sign, and missed; the two latter groups are defined "actionable." Statistics included chi-square, Fisher's exact, McNemar's, and Mann-Whitney U tests.

RESULTS

Discordant rate (cancer missed by one reader) for screen-detected cancers was overall comparable (DBT (31% [71/227]) and DM (30% [52/175]), p = .81), significantly lower at DBT for spiculated cancers (DBT, 19% [20/106] vs. DM, 36% [38/106], p = .003), but high (28/49 = 57%, p = 0.001) for DBT-only detected spiculated cancers. Reading time and sensitivity varied among readers. False-negative DBT-only detected spiculated cancers had shorter reading time than true-negatives in 46% (13/28). Retrospective evaluation classified the following DBT exams "actionable": three missed by both readers, 95% (39/41) of discordant cancers detected by both modes, all 30 discordant DBT-only cancers, 25% (13/51) of interval cancers.

CONCLUSIONS

Discordant rate was overall comparable for DBT and DM, significantly lower at DBT for spiculated cancers, but high for DBT-only detected spiculated lesions. Most false-negative screen-detected DBT were classified as "actionable."

CLINICAL RELEVANCE STATEMENT

Retrospective evaluation of false-negative interpretations from the Oslo Tomosynthesis Screening Trial shows that most discordant and several interval cancers could have been detected at screening. This underlines the potential for modern AI-based reading aids and triage, as high-volume screening is a demanding task.

KEY POINTS

• Digital breast tomosynthesis (DBT) screening is more sensitive and has higher specificity compared to digital mammography screening, but high-volume DBT screening is a demanding task which can result in high discordance rate among readers. • Independent double reading DBT screening had overall comparable discordance rate as digital mammography, lower for spiculated masses seen on both modalities, and higher for small spiculated cancer seen only on DBT. • Almost all discordant digital breast tomosynthesis-detected cancers (72 of 74) and 25% (13 of 51) of the interval cancers in the Oslo Tomosynthesis Screening Trial were retrospectively classified as actionable and could have been detected by the readers.

Effect of artificial intelligence-based computer-aided diagnosis on the screening outcomes of digital mammography: a matched cohort study

OBJECTIVE

To investigate whether artificial intelligence-based computer-aided diagnosis (AI-CAD) can improve radiologists' performance when used to support radiologists' interpretation of digital mammography (DM) in breast cancer screening.

METHODS

A retrospective database search identified 3158 asymptomatic Korean women who consecutively underwent screening DM between January and December 2019 without AI-CAD support, and screening DM between February and July 2020 with image interpretation aided by AI-CAD in a tertiary referral hospital using single reading. Propensity score matching was used to match the DM with AI-CAD group in a 1:1 ratio with the DM without AI-CAD group according to age, breast density, experience level of the interpreting radiologist, and screening round. Performance measures were compared with the McNemar test and generalized estimating equations.

RESULTS

A total of 1579 women who underwent DM with AI-CAD were matched with 1579 women who underwent DM without AI-CAD. Radiologists showed higher specificity (96% [1500 of 1563] vs 91.6% [1430 of 1561]; p < 0.001) and lower abnormal interpretation rates (AIR) (4.9% [77 of 1579] vs 9.2% [145 of 1579]; p < 0.001) with AI-CAD than without. There was no significant difference in the cancer detection rate (CDR) (AI-CAD vs no AI-CAD, 8.9 vs 8.9 per 1000 examinations; p = 0.999), sensitivity (87.5% vs 77.8%; p = 0.999), and positive predictive value for biopsy (PPV3) (35.0% vs 35.0%; p = 0.999) according to AI-CAD support.

CONCLUSIONS

AI-CAD increases the specificity for radiologists without decreasing sensitivity as a supportive tool in the single reading of DM for breast cancer screening.

CLINICAL RELEVANCE STATEMENT

This study shows that AI-CAD could improve the specificity of radiologists' DM interpretation in the single reading system without decreasing sensitivity, suggesting that it can benefit patients by reducing false positive and recall rates.

KEY POINTS

• In this retrospective-matched cohort study (DM without AI-CAD vs DM with AI-CAD), radiologists showed higher specificity and lower AIR when AI-CAD was used to support decision-making in DM screening. • CDR, sensitivity, and PPV for biopsy did not differ with and without AI-CAD support.

Screening outcome for interpretation by the first and second reader in a population-based mammographic screening program with independent double reading

BACKGROUND

Double reading of screening mammograms is associated with a higher rate of screen-detected cancer than single reading, but different strategies exist regarding reader pairing and blinding. Knowledge about these aspects is important when considering strategies for future use of artificial intelligence in mammographic screening.

PURPOSE

To investigate screening outcome, histopathological tumor characteristics, and mammographic features stratified by the first and the second reader in a population based screening program for breast cancer.

MATERIAL AND METHODS

The study sample consisted of data from 3,499,048 screening examinations from 834,691 women performed during 1996-2018 in BreastScreen Norway. All examinations were interpreted independently by two radiologists, 272 in total. We analyzed interpretation score, recall, and cancer detection, as well as histopathological tumor characteristics and mammographic features of the cancers, stratified by the first and second readers.

RESULTS

For Reader 1, the rate of positive interpretations was 4.8%, recall 2.3%, and cancer detection 0.5%. The corresponding percentages for Reader 2 were 4.9%, 2.5%, and 0.5% (P < 0.05 compared with Reader 1). No statistical difference was observed for histopathological tumor characteristics or mammographic features when stratified by Readers 1 and 2. Recall and cancer detection were statistically higher and histopathological tumor characteristics less favorable for cases detected after concordant positive compared with discordant interpretations.

CONCLUSION

Despite reaching statistical significance, mainly due to the large study sample, we consider the differences in interpretation scores, recall, and cancer detection between the first and second readers to be clinically negligible. For practical and clinical purposes, double reading in BreastScreen Norway is independent.

Breast cancer missed at screening; hindsight or mistakes?

PURPOSE

To investigate radiologists' interpretation scores of screening mammograms prior to diagnosis of screen-detected and interval breast cancers retrospectively classified as missed or true negative.

METHODS

We included data on radiologists' interpretation scores at screening prior to diagnosis for 1223 screen-detected and 1007 interval cancer cases classified as missed or true negative in an informed consensus-based review. All prior screening examinations were independently scored 1-5 by two radiologists; score 1 by both was considered concordant negative, score ≥ 2 by one radiologist discordant, and score ≥ 2 by both concordant positive. We analyzed associations between interpretation, review categories, mammographic features and histopathological findings using descriptive statistics and logistic regression.

RESULTS

Among screen-detected cancers, 31% of missed and 10% of true negative cancers had discordant or concordant positive interpretation at prior screening. The corresponding percentages for interval cancer were 21% and 8%. Age-adjusted odds ratio (OR) and 95% confidence interval (CI) for missed screen-detected cancer was 3.8 (95% CI: 2.6-5.4) after discordant and 5.5 (95% CI: 3.2-9.5) after concordant positive interpretation, using concordant negative as reference. Corresponding ORs for missed interval cancer were 3.0 (95% CI: 2.0-4.5) for discordant and 6.3 (95% CI: 2.3-17.5) for concordant positive interpretation. Asymmetry was the dominating mammographic feature at prior screening for all, except concordant positive screen-detected cancers where a mass dominated. Histopathological characteristics did not vary statistically with interpretation.

CONCLUSIONS

Most cancers were interpreted negatively at screening prior to diagnosis. Increased risk for missed screen-detected or interval cancer was observed after positive interpretation at prior screening.

Artificial intelligence in BreastScreen Norway: a retrospective analysis of a cancer-enriched sample including 1254 breast cancer cases

OBJECTIVES

To compare results of selected performance measures in mammographic screening for an artificial intelligence (AI) system versus independent double reading by radiologists.

METHODS

In this retrospective study, we analyzed data from 949 screen-detected breast cancers, 305 interval cancers, and 13,646 negative examinations performed in BreastScreen Norway during the period from 2010 to 2018. An AI system scored the examinations from 1 to 10, based on the risk of malignancy. Results from the AI system were compared to screening results after independent double reading. AI score 10 was set as the threshold. The results were stratified by mammographic density.

RESULTS

A total of 92.7% of the screen-detected and 40.0% of the interval cancers had an AI score of 10. Among women with a negative screening outcome, 9.1% had an AI score of 10. For women with the highest breast density, the AI system scored 100% of the screen-detected cancers and 48.6% of the interval cancers with an AI score of 10, which resulted in a sensitivity of 80.9% for women with the highest breast density for the AI system, compared to 62.8% for independent double reading. For women with screen-detected cancers who had prior mammograms available, 41.9% had an AI score of 10 at the prior screening round.

CONCLUSIONS

The high proportion of cancers with an AI score of 10 indicates a promising performance of the AI system, particularly for women with dense breasts. Results on prior mammograms with AI score 10 illustrate the potential for earlier detection of breast cancers by using AI in screen-reading.

KEY POINTS

• The AI system scored 93% of the screen-detected cancers and 40% of the interval cancers with AI score 10. • The AI system scored all screen-detected cancers and almost 50% of interval cancers among women with the highest breast density with AI score 10. • About 40% of the screen-detected cancers had an AI score of 10 on the prior mammograms, indicating a potential for earlier detection by using AI in screen-reading.

Artificial Intelligence Evaluation of 122 969 Mammography Examinations from a Population-based Screening Program

Background Artificial intelligence (AI) has shown promising results for cancer detection with mammographic screening. However, evidence related to the use of AI in real screening settings remain sparse. Purpose To compare the performance of a commercially available AI system with routine, independent double reading with consensus as performed in a population-based screening program. Furthermore, the histopathologic characteristics of tumors with different AI scores were explored. Materials and Methods In this retrospective study, 122 969 screening examinations from 47 877 women performed at four screening units in BreastScreen Norway from October 2009 to December 2018 were included. The data set included 752 screen-detected cancers (6.1 per 1000 examinations) and 205 interval cancers (1.7 per 1000 examinations). Each examination had an AI score between 1 and 10, where 1 indicated low risk of breast cancer and 10 indicated high risk. Threshold 1, threshold 2, and threshold 3 were used to assess the performance of the AI system as a binary decision tool (selected vs not selected). Threshold 1 was set at an AI score of 10, threshold 2 was set to yield a selection rate similar to the consensus rate (8.8%), and threshold 3 was set to yield a selection rate similar to an average individual radiologist (5.8%). Descriptive statistics were used to summarize screening outcomes. Results A total of 653 of 752 screen-detected cancers (86.8%) and 92 of 205 interval cancers (44.9%) were given a score of 10 by the AI system (threshold 1). Using threshold 3, 80.1% of the screen-detected cancers (602 of 752) and 30.7% of the interval cancers (63 of 205) were selected. Screen-detected cancer with AI scores not selected using the thresholds had favorable histopathologic characteristics compared to those selected; opposite results were observed for interval cancer. Conclusion The proportion of screen-detected cancers not selected by the artificial intelligence (AI) system at the three evaluated thresholds was less than 20%. The overall performance of the AI system was promising according to cancer detection. © RSNA, 2022.

Screen-detected and interval breast cancer after concordant and discordant interpretations in a population based screening program using independent double reading

OBJECTIVES

To analyze rates, odds ratios (OR), and characteristics of screen-detected and interval cancers after concordant and discordant initial interpretations and consensus in a population-based screening program.

METHODS

Data were extracted from the Cancer Registry of Norway for 487,118 women who participated in BreastScreen Norway, 2006-2017, with 2 years of follow-up. All mammograms were independently interpreted by two radiologists, using a score from 1 (negative) to 5 (high suspicion of cancer). A score of 2+ by one of the two radiologists was defined as discordant and 2+ by both radiologists as concordant positive. Consensus was performed on all discordant and concordant positive, with decisions of recall for further assessment or dismiss. OR was estimated with logistic regression with 95% confidence interval (CI), and histopathological tumor characteristics were analyzed for screen-detected and interval cancer.

RESULTS

Among screen-detected cancers, 23.0% (697/3024) had discordant scores, while 12.8% (117/911) of the interval cancers were dismissed at index screening. Adjusted OR was 2.4 (95% CI: 1.9-2.9) for interval cancer and 2.8 (95% CI: 2.5-3.2) for subsequent screen-detected cancer for women dismissed at consensus compared to women with concordant negative scores. We found 3.4% (4/117) of the interval cancers diagnosed after being dismissed to be DCIS, compared to 20.3% (12/59) of those with false-positive result after index screening.

CONCLUSION

Twenty-three percent of the screen-detected cancers was scored negative by one of the two radiologists. A higher odds of interval and subsequent screen-detected cancer was observed among women dismissed at consensus compared to concordant negative scores. Our findings indicate a benefit of personalized follow-up.

KEY POINTS

• In this study of 487,118 women participating in a screening program using independent double reading with consensus, 23% screen-detected cancers were detected by only one of the two radiologists. • The adjusted odds ratio for interval cancer was 2.4 (95% confidence interval: 1.9, 2.9) for cases dismissed at consensus using concordant negative interpretations as the reference. • Interval cancers diagnosed after being dismissed at consensus or after concordant negative scores had clinically less favorable prognostic tumor characteristics compared to those diagnosed after false-positive results.

True and Missed Interval Cancer in Organized Mammographic Screening: A Retrospective Review Study of Diagnostic and Prior Screening Mammograms

RATIONALE AND OBJECTIVES

To explore radiological aspects of interval breast cancer in a population-based screening program.

MATERIALS AND METHODS

We performed a consensus-based informed review of mammograms from diagnosis and prior screening from women diagnosed with interval cancer 2004-2016 in BreastScreen Norway. Cases were classified as true (no findings on prior screening mammograms), occult (no findings at screening or diagnosis), minimal signs (minor/non-specific findings) and missed (obvious findings). We analyzed mammographic findings, density, time since prior screening, and histopathological characteristics between the classification groups.

RESULTS

The study included 1010 interval cancer cases. Mean age at diagnosis was 61 years (SD = 6), mean time between screening and diagnosis 14 months (SD = 7). A total of 48% (479/1010) were classified as true or occult, 28% (285/1010) as minimal signs and 24% (246/1010) as missed. We observed no differences in mammographic density between the groups, except from a higher percentage of dense breasts in women with occult cancer. Among cancers classified as missed, about 1/3 were masses and 1/3 asymmetries at prior screening. True interval cancers were diagnosed later in the screening interval than the other classification categories. No differences in histopathological characteristics were observed between true, minimal signs and missed cases.

CONCLUSION

In an informed review, 24% of the interval cancers were classified as missed based on visibility and mammographic findings on prior screening mammograms. Three out of four true interval cancers were diagnosed in the second year of the screening interval. We observed no statistical differences in histopathological characteristics between true and missed interval cancers.

Time Requirement and Feasibility of a Systematic Quality Peer Review of Reporting in Radiology

OBJECTIVE

 To estimate the human resources required for a retrospective quality review of different percentages of all routine diagnostic procedures in the Department of Radiology at Bern University Hospital, Switzerland.

MATERIALS AND METHODS

 Three board-certified radiologists retrospectively evaluated the quality of the radiological reports of a total of 150 examinations (5 different examination types: abdominal CT, chest CT, mammography, conventional X-ray images and abdominal MRI). Each report was assigned a RADPEER score of 1 to 3 (score 1: concur with previous interpretation; score 2: discrepancy in interpretation/not ordinarily expected to be made; score 3: discrepancy in interpretation/should be made most of the time). The time (in seconds, s) required for each review was documented and compared. A sensitivity analysis was conducted to calculate the total workload for reviewing different percentages of the total annual reporting volume of the clinic.

RESULTS

 Among the total of 450 reviews analyzed, 91.1 % (410/450) were assigned a score of 1 and 8.9 % (40/450) were assigned scores of 2 or 3. The average time (in seconds) required for a peer review was 60.4 s (min. 5 s, max. 245 s). The reviewer with the greatest clinical experience needed significantly less time for reviewing the reports than the two reviewers with less clinical expertise (p < 0.05). Average review times were longer for discrepant ratings with a score of 2 or 3 (p < 0.05). The total time requirement calculated for reviewing all 5 types of examination for one year would be more than 1200 working hours.

CONCLUSION

 A retrospective peer review of reports of radiological examinations using the RADPEER system requires considerable human resources. However, to improve quality, it seems feasible to peer review at least a portion of the total yearly reporting volume.

KEY POINTS

  · A systematic retrospective assessment of the content of radiological reports using the RADPEER system involves high personnel costs.. · The retrospective assessment of all reports of a clinic or practice seems unrealistic due to the lack of highly specialized personnel.. · At least part of all reports should be reviewed with the aim of improving the quality of reports..

CITATION FORMAT

· Maurer MH, Brönnimann M, Schroeder C et al. Time Requirement and Feasibility of a Systematic Quality Peer Review of Reporting in Radiology. Fortschr Röntgenstr 2021; 193: 160 - 167.

Consensus Review of Discordant Imaging Findings after the Introduction of Digital Screening Mammography: Irish National Breast Cancer Screening Program Experience

Background When there are discordant results between individual readers interpreting screening mammograms, consensus by independent readers may reduce unnecessary recalls for further work-up. Few studies have looked at consensus outcomes following the introduction of full-field digital mammography (FFDM). Purpose To determine outcomes of women discussed at consensus meetings during a 5-year period after introduction of FFDM, including recall rates, cancer detection, and interval cancers. Materials and Methods In this retrospective study from January 2010 to December 2014, the authors reviewed all screening mammograms from a single unit of a biennial Irish national breast screening program after the introduction of FFDM. Screening mammograms were double reported. Abnormalities detected at discordant screening mammography readings were discussed at biweekly consensus meetings. Outcomes of consensus meetings were reviewed in terms of referral for assessment, biopsy rates, cancer detection, and outcomes from later rounds of screening. Statistical analysis was performed by using a χ² test to compare recall rate and cancer detection rates between FFDM and screen-film mammography based on a previously published study from the authors' institution. Results A total of 2565 women (age range, 50-64 years) with discordant mammographic findings were discussed at consensus meetings. Of these 2565 women, 1037 (40%) were referred for further assessment; 108 cancers were detected in these women. Of the 1285 women who returned to biennial screening, malignancy was detected at the site of original concern in 12 women at a further round of screening. Three true interval cancers were identified. Sensitivity (88.5% [108 of 122]; 95% confidence interval [CI]: 81.5%, 93.6%) and negative predictive value (99.1% [1528 of 1542]; 95% CI: 98.5%, 99.4%) of consensus review remained stable after the introduction of FFDM. Specificity of consensus review increased from 57.6% (729 of 1264; 95% CI: 54.9%, 60.4%) to 62.2% (1528 of 2457; 95% CI: 60.2%, 64.1%) (P = .008). Conclusion Consensus review of discordant mammographic screening-detected abnormalities remains a valuable tool after introduction of full-field digital mammography as it reduces recall for assessment and demonstrates persistently high sensitivity and negative predictive values. © RSNA, 2020 See also the editorial by Hofvind and Lee in this issue.

Double Reading in Breast Cancer Screening: Cohort Evaluation in the CO-OPS Trial

Purpose To investigate the effect of double readings by a second radiologist on recall rates, cancer detection, and characteristics of cancers detected in the National Health Service Breast Screening Program in England. Materials and Methods In this retrospective analysis, 805 206 women were evaluated through screening and diagnostic test results by extracting 1 year of routine data from 33 English breast screening centers. Centers used double reading of digital mammograms, with arbitration if there were discrepant interpretations. Information on reader decisions, with results of follow-up tests, were used to explore the effect of the second reader. The statistical tests used were the test for equality of proportions, the χ2 test for independence, and the t test. Results The first reader recalled 4.76% of women (38 295 of 805 206 women; 95% confidence interval [CI]: 4.71%, 4.80%). Two readers recalled 6.19% of women in total (49 857 of 805 206 women; 95% CI: 6.14%, 6.24%), but arbitration of discordant readings reduced the recall rate to 4.08% (32 863 of 805 206 women; 95% CI: 4.04%, 4.12%; P < .001). A total of 7055 cancers were detected, of which 627 (8.89%; 95% CI: 8.22%, 9.55%; P < .001) were detected by the second reader only. These additional cancers were more likely to be ductal carcinoma in situ (30.5% [183 of 600] vs 22.0% [1344 of 6114]; P < .001), and additional invasive cancers were smaller (mean size, 14.2 vs 16.7 mm; P < .001), had fewer involved nodes, and were likely to be lower grade. Conclusion Double reading with arbitration reduces recall and increases cancer detection compared with single reading. Cancers detected only by the second reader were smaller, of lower grade, and had less nodal involvement. © RSNA, 2018.

Usefulness of grayscale inverted images in addition to standard images in digital mammography

BACKGROUND

Mammography is essential for early diagnosis of breast cancer, which is the most common type of cancer in females that is associated with a high mortality rate. We investigated whether evaluation of the grayscale inverted images of mammograms would aid in increasing the diagnostic sensitivity of the mammographic imaging technique.

METHODS

Our study included 636 mammograms of 159 women who had undergone digital mammography. Standard, grayscale inverted, and standard plus grayscale inverted images were sequentially examined three times, at 15-day intervals, for the presence or assessment of pathological changes in the skin, calcification, asymmetric density, mass lesions, structural distortions, and intramammary and axillary lymph nodes. To determine whether grayscale inverted image assessment improved detection rates, the results of the three assessment modes were compared using Cochran's Q test and the McNemar test (p < 0.05 was considered statistically significant).

RESULTS

The average age of 159 patients was 50.4 years (range, 35-80 years). There were significant differences among the three assessment modes with respect to calcification and intramammary lymph nodes (p < 0.05); however, no significant differences were observed for the detection of other parameters.

CONCLUSIONS

Assessment of grayscale inverted images in addition to standard images facilitates the detection of microcalcification.

Microcalcification on mammography: approaches to interpretation and biopsy

This article discusses the significance of microcalcifications on mammography and the changes in technology that have influenced management; it also describes a pragmatic approach to investigation of microcalcification in a UK screening programme.

Tumour cell invasion into blood vessels is significantly related to breast cancer subtypes and decreased survival

AIMS

Vascular invasion in breast cancer is associated with increased risk of recurrence, metastases and death from disease. However, there are few studies discriminating between blood vessel invasion (BVI) and lymphatic vessel involvement (LVI).

METHODS

A population-based series of 282 breast cancers was examined (200 screen-detected and 82 interval patients) with respect to BVI and LVI in addition to basic features and molecular subtypes, using CD31 and D2-40 antibodies. This series is part of the prospective Norwegian Breast Cancer Screening Program.

RESULTS

The frequency of LVI and BVI was 25% and 15%, respectively. BVI was associated with HER2-positive and basal-like tumours, and several features of aggressive breast cancer, whereas LVI showed weaker associations. BVI was the strongest factor to predict interval cancer presentation. BVI showed significant associations with recurrence-free survival and disease-specific survival in univariate and multivariate analyses, whereas LVI was not significant.

CONCLUSIONS

Our findings indicate that BVI by tumour cells is strongly associated with aggressive tumour features including a basal-like phenotype, and BVI was an independent prognostic factor in contrast to what was found for LVI.

Cost-Effectiveness of Double Reading versus Single Reading of Mammograms in a Breast Cancer Screening Programme

OBJECTIVES

The usual practice in breast cancer screening programmes for mammogram interpretation is to perform double reading. However, little is known about its cost-effectiveness in the context of digital mammography. Our purpose was to evaluate the cost-effectiveness of double reading versus single reading of digital mammograms in a population-based breast cancer screening programme.

METHODS

Data from 28,636 screened women was used to establish a decision-tree model and to compare three strategies: 1) double reading; 2) double reading for women in their first participation and single reading for women in their subsequent participations; and 3) single reading. We calculated the incremental cost-effectiveness ratio (ICER), which was defined as the expected cost per one additionally detected cancer. We performed a deterministic sensitivity analysis to test the robustness of the ICER.

RESULTS

The detection rate of double reading (5.17‰) was similar to that of single reading (4.78‰; P = .768). The mean cost of each detected cancer was €8,912 for double reading and €8,287 for single reading. The ICER of double reading versus single reading was €16,684. The sensitivity analysis showed variations in the ICER according to the sensitivity of reading strategies. The strategy that combines double reading in first participation with single reading in subsequent participations was ruled out due to extended dominance.

CONCLUSIONS

From our results, double reading appears not to be a cost-effective strategy in the context of digital mammography. Double reading would eventually be challenged in screening programmes, as single reading might entail important net savings without significantly changing the cancer detection rate. These results are not conclusive and should be confirmed in prospective studies that investigate long-term outcomes like quality adjusted life years (QALYs).

Evaluation of 12 strategies for obtaining second opinions to improve interpretation of breast histopathology: simulation study

OBJECTIVE

 To evaluate the potential effect of second opinions on improving the accuracy of diagnostic interpretation of breast histopathology.

DESIGN

 Simulation study.

SETTING

 12 different strategies for acquiring independent second opinions.

PARTICIPANTS

 Interpretations of 240 breast biopsy specimens by 115 pathologists, one slide for each case, compared with reference diagnoses derived by expert consensus.

MAIN OUTCOME MEASURES

 Misclassification rates for individual pathologists and for 12 simulated strategies for second opinions. Simulations compared accuracy of diagnoses from single pathologists with that of diagnoses based on pairing interpretations from first and second independent pathologists, where resolution of disagreements was by an independent third pathologist. 12 strategies were evaluated in which acquisition of second opinions depended on initial diagnoses, assessment of case difficulty or borderline characteristics, pathologists' clinical volumes, or whether a second opinion was required by policy or desired by the pathologists. The 240 cases included benign without atypia (10% non-proliferative, 20% proliferative without atypia), atypia (30%), ductal carcinoma in situ (DCIS, 30%), and invasive cancer (10%). Overall misclassification rates and agreement statistics depended on the composition of the test set, which included a higher prevalence of difficult cases than in typical practice.

RESULTS

 Misclassification rates significantly decreased (P<0.001) with all second opinion strategies except for the strategy limiting second opinions only to cases of invasive cancer. The overall misclassification rate decreased from 24.7% to 18.1% when all cases received second opinions (P<0.001). Obtaining both first and second opinions from pathologists with a high volume (≥10 breast biopsy specimens weekly) resulted in the lowest misclassification rate in this test set (14.3%, 95% confidence interval 10.9% to 18.0%). Obtaining second opinions only for cases with initial interpretations of atypia, DCIS, or invasive cancer decreased the over-interpretation of benign cases without atypia from 12.9% to 6.0%. Atypia cases had the highest misclassification rate after single interpretation (52.2%), remaining at more than 34% in all second opinion scenarios.

CONCLUSION

 Second opinions can statistically significantly improve diagnostic agreement for pathologists' interpretations of breast biopsy specimens; however, variability in diagnosis will not be completely eliminated, especially for breast specimens with atypia.

Double versus single reading of mammograms in a breast cancer screening programme: a cost-consequence analysis

OBJECTIVES

To assess the costs and health-related outcomes of double versus single reading of digital mammograms in a breast cancer screening programme.

METHODS

Based on data from 57,157 digital screening mammograms from women aged 50-69 years, we compared costs, false-positive results, positive predictive value and cancer detection rate using four reading strategies: double reading with and without consensus and arbitration, and single reading with first reader only and second reader only. Four highly trained radiologists read the mammograms.

RESULTS

Double reading with consensus and arbitration was 15 % (Euro 334,341) more expensive than single reading with first reader only. False-positive results were more frequent at double reading with consensus and arbitration than at single reading with first reader only (4.5 % and 4.2 %, respectively; p < 0.001). The positive predictive value (9.3 % and 9.1 %; p = 0.812) and cancer detection rate were similar for both reading strategies (4.6 and 4.2 per 1000 screens; p = 0.283).

CONCLUSIONS

Our results suggest that changing to single reading of mammograms could produce savings in breast cancer screening. Single reading could reduce the frequency of false-positive results without changing the cancer detection rate. These results are not conclusive and cannot be generalized to other contexts with less trained radiologists.

KEY POINTS

• Double reading of digital mammograms is more expensive than single reading. • Compared to single reading, double reading yields a higher proportion of false-positive results. • The cancer detection rate was similar for double and single readings. • Single reading may be a cost-effective strategy in breast cancer screening programmes.

Double reading rates and quality assurance practices in Norwegian hospital radiology departments: two parallel national surveys

BACKGROUND

Double reading as a quality assurance (QA) tool is employed extensively in Norwegian hospital radiology departments. The practice is resource consuming and regularly debated.

PURPOSE

To investigate the rates of double reading in Norwegian hospital radiology departments, to identify department characteristics associated with double reading rates, and to investigate associations between double reading and other quality improvement.

MATERIAL AND METHODS

We issued two parallel national surveys to management and to consultant radiologists, respectively. Management was defined as the chief medical officer and/or the head of the radiology department. The management survey covered staffing, perceived resource situation, double reading, guidelines, and quality improvement. The radiologist survey served to validate management responses concerning double reading. Management survey items concerning practices of quality improvement were organized into three indices reflecting different quality approaches, namely: appropriateness of investigations; personal performance feedback; and system performance feedback.

RESULTS

The response rates of the surveys were 100% (45/45) for management and 55% (266/483) for radiologists. Of all exams read by consultants, 33% were double read. The double reading rate was highest in university hospital departments (59%), intermediate in other teaching departments (30%), and lowest in non-teaching departments (11%) (P = 0.01). Among the quality indices, mean scores were highest on appropriateness index (68%), intermediate on the person index (56%), and lowest on system index (37%). There were no correlations between double reading rates and scores on any of the quality indices.

CONCLUSION

The rate of double reading in Norwegian hospital radiology is significantly correlated to department teaching status, but not to other practices of quality work.

Second opinion in breast pathology: policy, practice and perception

AIMS

To assess the laboratory policies, pathologists' clinical practice and perceptions about the value of second opinions for breast pathology cases among pathologists practising in the USA.

METHODS

Cross-sectional data were collected from 252 pathologists who interpret breast specimens in eight states using a web-based survey. Descriptive statistics were used to characterise findings.

RESULTS

Most participants had >10 years of experience interpreting breast specimens (64%), were not affiliated with academic centres (73%) and were not considered experts by their peers (79%). Laboratory policies mandating second opinions varied by diagnosis: invasive cancer 65%; ductal carcinoma in situ (DCIS) 56%; atypical ductal hyperplasia 36% and other benign cases 33%. 81% obtained second opinions in the absence of policies. Participants believed they improve diagnostic accuracy (96%) and protect from malpractice suits (83%), and were easy to obtain, did not take too much time and did not make them look less adequate. The most common (60%) approach to resolving differences between the first and second opinion is to ask for a third opinion, followed by reaching a consensus.

CONCLUSIONS

Laboratory-based second opinion policies vary for breast pathology but are most common for invasive cancer and DCIS cases. Pathologists have favourable attitudes towards second opinions, adhere to policies and obtain them even when policies are absent. Those without a formal policy may benefit from supportive clinical practices and systems that help obtain second opinions.

The cumulative risk of false-positive screening results across screening centres in the Norwegian Breast Cancer Screening Program

BACKGROUND

Recall for assessment in mammographic screening entails an inevitable number of false-positive screening results. This study aimed to investigate the variation in the cumulative risk of a false positive screening result and the positive predictive value across the screening centres in the Norwegian Breast Cancer Screening Program.

METHODS

We studied 618,636 women aged 50-69 years who underwent 2,090,575 screening exams (1996-2010. Recall rate, positive predictive value, rate of screen-detected cancer, and the cumulative risk of a false positive screening result, without and with invasive procedures across the screening centres were calculated. Generalized linear models were used to estimate the probability of a false positive screening result and to compute the cumulative false-positive risk for up to ten biennial screening examinations.

RESULTS

The cumulative risk of a false-positive screening exam varied from 10.7% (95% CI: 9.4-12.0%) to 41.5% (95% CI: 34.1-48.9%) across screening centres, with a highest to lowest ratio of 3.9 (95% CI: 3.7-4.0). The highest to lowest ratio for the cumulative risk of undergoing an invasive procedure with a benign outcome was 4.3 (95% CI: 4.0-4.6). The positive predictive value of recall varied between 12.0% (95% CI: 11.0-12.9%) and 19.9% (95% CI: 18.3-21.5%), with a highest to lowest ratio of 1.7 (95% CI: 1.5-1.9).

CONCLUSIONS

A substantial variation in the performance measures across the screening centres in the Norwegian Breast Cancer Screening Program was identified, despite of similar administration, procedures, and quality assurance requirements. Differences in the readers' performance is probably of influence for the variability. This results underscore the importance of continuous surveillance of the screening centres and the radiologists in order to sustain and improve the performance and effectiveness of screening programs.

Mammographic performance in a population-based screening program: before, during, and after the transition from screen-film to full-field digital mammography

PURPOSE

To compare performance measures before, during, and after the transition from screen-film mammography (SFM) to full-field digital mammography (FFDM) in a population-based screening program.

MATERIALS AND METHODS

No institutional review board approval was required for this analysis involving anonymized data for women aged 50-69 years enrolled in the Norwegian Breast Cancer Screening Program during 1996-2010. The χ(2) test was used to examine the equality of proportions of recall rates, positive predictive value of recall examinations and of invasive procedures, in addition to rates of screening-detected and interval cancers in women initially screened with SFM and FFDM and for women subsequently screened with SFM after SFM, FFDM after SFM, and FFDM after FFDM.

RESULTS

The recall rate was 3.4% (47 091 of 1 391 188) for SFM and 2.9% (13 130 of 446 172) for FFDM (P < .001). The biopsy rate was 1.4% (19 776 of 1 391 188) for SFM and 1.1% (5108 of 446 172) for FFDM (P < .001). The rate of screening-detected ductal carcinoma in situ was higher (P = .019) while the rate of invasive breast cancer was lower (P < .001) for FFDM compared with those for SFM. The rate of both invasive screening-detected and interval breast cancer remained stable during the transition from SFM to FFDM (when the previous examination was SFM) and after FFDM was firmly established (when the previous examination was FFDM, >25 months after FFDM adoption) (P < .05). The positive predictive value of recall examinations and of invasive procedures increased from 19.3% (4559 of 23 598) and 48.3% (4651 of 9623) to 22.7% (681 of 2995) and 57.5% (689 of 1198), respectively, after adoption of FFDM (P < .001).

CONCLUSION

After the initial transitional phase from SFM to FFDM, population-based screening with FFDM is associated with less harm because of lower recall and biopsy rates and higher positive predictive values after biopsy than screening with SFM.

The cumulative risk of false-positive results in the Norwegian Breast Cancer Screening Program: updated results

BACKGROUND

Some false-positive results are inevitable in mammographic screening, but the impact of false-positive findings on the program and the participants is a disadvantage of screening. The objective of the current study was to estimate the cumulative risk of a false-positive result over 10 biennial screening examinations and the cumulative risk of undergoing an invasive procedure with a benign outcome in women screened between the ages of 50 years to 69 years.

METHODS

A retrospective cohort study was performed in 231,310 women aged 50 years to 51 years at the time of first mammography screening who underwent 715,311 screening mammograms in the Norwegian Breast Cancer Screening Program from 1996 through 2010. Generalized linear mixed models were used to estimate the probability of a false-positive screening result and to compute the cumulative false-positive risk for up to 10 biennial screening examinations.

RESULTS

The cumulative false-positive risk after 20 years of biennial screening for women who initiated screening aged 50 years to 51 years was 20.0% (95% confidence interval [95% CI], 19.7%-20.4%). The cumulative risk of undergoing an invasive procedure with a benign outcome for the same group of women was 4.1% (95% CI, 3.9%-4.3%). The cumulative risk of undergoing a fine-needle aspiration cytology, core needle biopsy, or open biopsy with a benign outcome was 1.4% (95% CI, 1.3%-1.5%), 2.0% (95% CI, 1.9%-2.1%), and 0.16% (95% CI, 0.13%-0.19%), respectively.

CONCLUSIONS

One in every 5 women will be recalled for further assessment with a negative outcome if they attend biennial mammographic screening between ages 50 years to 69 years. The risk of an invasive procedure with a benign outcome is approximately 4%. It is important to communicate the existence and extent of this risk to the target group and to reduce to a minimum the waiting times between screening and further assessment.

Performance of double reading mammography in an Iranian population and its effect on patient outcome

Background

Considering the importance and responsibility of reporting mammography and the necessity to notice details with a high degree of precision, double reading mammography has been introduced and recommended.

Objectives

This study aimed to assess the performance of double reading of mammograms and its effect on patient outcomes.

Patients and Methods

Throughout this cross sectional study, 1284 digitized mammographic views of 642 breasts which belonged to 339 women (of which 303 were bilateral and 36 were unilateral mammographies) were enrolled. Two independent radiologists interpreted these mammograms and BI-RADS categories of both reports were compared. Discordant results were determined and assumed significant if they were in the positive (BI-RADS 0, 4, 5) versus negative (BI-RADS 1, 2, 3) groups and then significant discordant cases were followed up to determine benign versus malignant final diagnosis. The recall rate was calculated for each reader. Inter-observer agreement in breast density was determined by Kappa test.

Results

Readers had consensus on BI-RADS categories in 459 breasts (71%), but diverse categories were used for 183 breasts (29%), including 132 significant and 51 non-significant discrepancies. According to weighted Kappa test, agreement between two readers in positive or negative reports was 0.78 (95% CI=0.73-0.83) and in parenchymal density, it was 0.73 (95% CI=0.7-0.77). Most of the discrepancies were between category zero versus categories 1 and 2 (63.4%). The recall rate was 36% for the first and 44% for the second reader. Among 132 significant discordant results, one case had the final diagnosis of malignancy and the others had benign or negative diagnosis. There was 0.2% increase in cancer detection rate by double reading.

Conclusion

This study shows no significant improvement in the cancer detection rate by double reading; however, a lower recall rate could be a more helpful consequence.

Prospective trial comparing full-field digital mammography (FFDM) versus combined FFDM and tomosynthesis in a population-based screening programme using independent double reading with arbitration

OBJECTIVES

To compare double readings when interpreting full field digital mammography (2D) and tomosynthesis (3D) during mammographic screening.

METHODS

A prospective, Ethical Committee approved screening study is underway. During the first year 12,621 consenting women underwent both 2D and 3D imaging. Each examination was independently interpreted by four radiologists under four reading modes: Arm A-2D; Arm B-2D + CAD; Arm C-2D + 3D; Arm D-synthesised 2D + 3D. Examinations with a positive score by at least one reader were discussed at an arbitration meeting before a final management decision. Paired double reading of 2D (Arm A + B) and 2D + 3D (Arm C + D) were analysed. Performance measures were compared using generalised linear mixed models, accounting for inter-reader performance heterogeneity (P < 0.05).

RESULTS

Pre-arbitration false-positive scores were 10.3 % (1,286/12,501) and 8.5 % (1,057/12,501) for 2D and 2D + 3D, respectively (P < 0.001). Recall rates were 2.9 % (365/12,621) and 3.7 % (463/12,621), respectively (P = 0.005). Cancer detection was 7.1 (90/12,621) and 9.4 (119/12,621) per 1,000 examinations, respectively (30 % increase, P < 0.001); positive predictive values (detected cancer patients per 100 recalls) were 24.7 % and 25.5 %, respectively (P = 0.97). Using 2D + 3D, double-reading radiologists detected 27 additional invasive cancers (P < 0.001).

CONCLUSION

Double reading of 2D + 3D significantly improves the cancer detection rate in mammography screening.

KEY POINTS

• Tomosynthesis-based screening was successfully implemented in a large prospective screening trial. • Double reading of tomosynthesis-based examinations significantly reduced false-positive interpretations. • Double reading of tomosynthesis significantly increased the detection of invasive cancers.

Teaching receiver operating characteristic analysis: an interactive laboratory exercise

RATIONALE AND OBJECTIVES

Despite its fundamental importance in the evaluation of diagnostic tests, receiver operating characteristic (ROC) analysis is not easily understood. The purpose of this project was to create a learning experience that resulted in an intuitive understanding of the basic principles of ROC analysis.

MATERIALS AND METHODS

An interactive laboratory exercise was developed for a class about radiology testing taught within a clinical epidemiology course between 2000 and 2009. The physician students in the course were clinical fellows from various medical specialties who were enrolled in a graduate degree program in clinical investigation. For the exercise, the class was divided into six groups. Each group interpreted radiographs from a set of 50 exams of the peripheral skeleton to determine the presence or absence of an acute fracture. Data from the class were pooled and given to each student. Students calculated the area under the ROC curve (AUC) corresponding to overall class performance. A binormal ROC curve was also fitted to the data from each class year.

RESULTS

The laboratory exercise was conducted for 8 years with approximately 20-30 students per year. The mean AUC over the eight laboratory classes was 0.72 with a standard deviation of 0.08 (range, 0.60-0.85).

CONCLUSION

With some simplifications in design, an observer study can be conducted in a laboratory classroom setting. Participatory data collection promotes the intuitive understanding of ROC analysis principles.

Sensitivity and specificity of mammographic screening as practised in Vermont and Norway

OBJECTIVE

The aim of this study was to examine the sensitivity and specificity of screening mammography as performed in Vermont, USA, and Norway.

METHODS

Incident screening data from 1997 to 2003 for female patients aged 50-69 years from the Vermont Breast Cancer Surveillance System (116 996 subsequent screening examinations) and the Norwegian Breast Cancer Screening Program (360 872 subsequent screening examinations) were compared. Sensitivity and specificity estimates for the initial (based on screening mammogram only) and final (screening mammogram plus any further diagnostic imaging) interpretations were directly adjusted for age using 5-year age intervals for the combined Vermont and Norway population, and computed for 1 and 2 years of follow-up, which ended at the time of the next screening mammogram.

RESULTS

For the 1-year follow-up, sensitivities for initial assessments were 82.0%, 88.2% and 92.5% for 1-, 2- and >2-year screening intervals, respectively, in Vermont (p=0.022). For final assessments, the values were 73.6%, 83.3% and 81.2% (p=0.047), respectively. For Norway, sensitivities for initial assessments were 91.0% and 91.3% (p=0.529) for 2- and >2-year intervals, and 90.7% and 91.3%, respectively, for final assessments (p=0.630). Specificity was lower in Vermont than in Norway for each screening interval and for all screening intervals combined, for both initial (90.6% vs 97.8% for all intervals; p<0.001) and final (98.8% vs 99.5% for all intervals; p<0.001) assessments.

CONCLUSION

Our study showed higher sensitivity and specificity in a biennial screening programme with an independent double reading than in a predominantly annual screening program with a single reading.

ADVANCES IN KNOWLEDGE

This study demonstrates that higher recall rates and lower specificity are not always associated with higher sensitivity of screening mammography. Differences in the screening processes in Norway and Vermont suggest potential areas for improvement in the latter.

Mammography screening using independent double reading with consensus: is there a potential benefit for computer-aided detection?

BACKGROUND

Double reading improves the cancer detection rate in mammography screening. Single reading with computer-aided detection (CAD) has been considered to be an alternative to double reading. Little is known about the potential benefit of CAD in breast cancer screening with double reading.

PURPOSE

To compare prospective independent double reading of screen-film (SFM) and full-field digital (FFDM) mammography in population-based screening with retrospective standalone CAD performance on the baseline mammograms of the screen-detected cancers and subsequent cancers diagnosed during the follow-up period.

MATERIAL AND METHODS

The study had ethics committee approval. A 5-point rating scale for probability of cancer was used for 23,923 (SFM = 16,983; FFDM = 6940) screening mammograms. Of 208 evaluable cancers, 104 were screen-detected and 104 were subsequent (44 interval and 60 next screening round) cancers. Baseline mammograms of subsequent cancers were retrospectively classified in consensus without information about cancer location, histology, or CAD prompting as normal, non-specific minimal signs, significant minimal signs, and false-negatives. The baseline mammograms of the screen-detected cancers and subsequent cancers were evaluated by CAD. Significant minimal signs and false-negatives were considered 'actionable' and potentially diagnosable if correctly prompted by CAD.

RESULTS

CAD correctly marked 94% (98/104) of the baseline mammograms of the screen-detected cancers (SFM = 95% [61/64]; FFDM = 93% [37/40]), including 96% (23/24) of those with discordant interpretations. Considering only those baseline examinations of subsequent cancers prospectively interpreted as normal and retrospectively categorized as 'actionable', CAD input at baseline screening had the potential to increase the cancer detection rate from 0.43% to 0.51% (P = 0.13); and to increase cancer detection by 16% ([104 + 17]/104) and decrease interval cancers by 20% (from 44 to 35).

CONCLUSION

CAD may have the potential to increase cancer detection by up to 16%, and to reduce the number of interval cancers by up to 20% in SFM and FFDM screening programs using independent double reading with consensus review. The influence of true- and false-positive CAD marks on decision-making can, however, only be evaluated in a prospective clinical study.

No benefit for consensus double reading at baseline screening for lung cancer with the use of semiautomated volumetry software

PURPOSE

To retrospectively evaluate the performance of consensus double reading compared with single reading at baseline screening of a lung cancer computed tomography (CT) screening trial.

MATERIALS AND METHODS

The study was approved by the Dutch Minister of Health and ethical committees. Written informed consent was obtained from all participants. The benefit of consensus double reading was expressed by the percentage change in cancer detection rate, recall rate, number of additional nodules detected, and change in sensitivity and specificity in 7557 participants. The reference standard was a retrospective analysis of the serial CT scans performed in participants diagnosed with lung cancer during a 2-year period after baseline. Semiautomated volumetric software was used for nodule evaluation. McNemar tests were performed to test statistical significance. In addition, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated and 95% confidence intervals (CIs) constructed.

RESULTS

Seventy-four cases of lung cancer were qualified as detectable at baseline. Compared with single reading, consensus double reading did not increase the cancer detection rate (2.7%; 95% CI: -1.0%, 6.4%; P = .50) or change the recall rate (20.6% vs 20.8%, P = .28), but led to the detection of 19.0% (1635 of 8623; 95% CI: 18.0%, 19.9%, P < .01) more nodules. The sensitivity, specificity, PPV, and NPV were 95.9% (71 of 74), 80.2% (6001 of 7483), 4.6% (71 of 1553) and 99.9% (6001 of 6004) for single reading and 98.6% (73 of 74), 80.0% (1497 of 7483), 4.6% (73 of 1570), and 99.9% (5986 of 5987) for consensus double reading, respectively.

CONCLUSION

There is no statistically significant benefit for consensus double reading at baseline screening for lung cancer with the use of a nodule management strategy based solely on semiautomated volumetry.

Quantification of the UK 5-point breast imaging classification and mapping to BI-RADS to facilitate comparison with international literature

OBJECTIVE

The UK 5-point breast imaging scoring system, recently formalised by the Royal College of Radiologists Breast Group, does not specify the likelihood of malignancy in each category. The breast imaging and reporting data system (BI-RADS) is widely used throughout North America and much of Europe. The main purpose of this study is to quantify the cancer likelihood of each of the UK 5-point categories and map them to comparable BI-RADS categories to facilitate comparison with North American and European literature and publication of UK research abroad.

METHODS

During the 8 year study period, mammogram and ultrasound results were UK scored and the percentage of cancer outcomes within each group calculated. These were then compared with the percentage incidence of the BI-RADS categories.

RESULTS

Of 23 741 separate assessment episodes, 15 288 mammograms and 10 642 ultrasound examinations were evaluated. There was a direct correlation between UK scoring and BI-RADS for categories 1 and 5. UK Score 2 lipomas and simple cysts correlated with BI-RADS 2, with the remaining UK Score 2 lesions (mostly fibroadenomas) assigned to BI-RADS 3. BI-RADS 4 incorporates a wide range of cancer risk (2-95%) with subdivisions a, b and c indicating increasing, but unspecified, likelihood of malignancy. UK Score 3 correlated with BI-RADS 4 a/b and UK Score 4 corresponded with BI-RADS 4c.

CONCLUSION

This study quantifies the cancer likelihood of the UK scoring and maps them to parallel BI-RADS categories, with equivalent cancer risks. This facilitates the ability to share UK research data and clinical practice on an international scale.

Double reading of radiological examinations in Norway

BACKGROUND

Double reading of images is a part of the quality assurance activities at many radiological centers.

PURPOSE

To investigate the extent of and routines for double reading in Norway and the institutional heads' attitudes toward double reading.

MATERIAL AND METHODS

A questionnaire was addressed to the heads of all radiological institutions in Norway. The questionnaire concerned staffing, examinations performed, extent of double reading per imaging modality (except mammography screening), guidelines for double reading, checks of completed radiology reports, frequency of regular quality assurance meetings to discuss missed findings, and the heads' attitudes toward double reading.

RESULTS

The response rate was 73% (53/73). The percentage across imaging modalities of examinations being double read was 41% overall: 56% at university hospitals, 37% at local hospitals, and 18% at private centers. Double reading was most common for positron emission tomography (PET)/PET-computed tomography (CT) examinations (100%), and clinical mammography (91%). Almost all examinations read by residents were double read. Only 15% of institutions had written guidelines for double reading, 15% performed random double readings of completed examinations, and 55% organized regular meetings to discuss missed findings. Forty-six percent of the institutional heads wanted an increased use of double reading.

CONCLUSION

Double reading is common in Norway, especially in residency training, mammography, and PET/PET-CT. It is less common at private centers. Established routines for double reading are scarce. Many institutional heads want more double reading. The potential of double reading to assure quality in radiology should be better exploited.

Missed and true interval and screen-detected breast cancers in a population based screening program

RATIONALE AND OBJECTIVES

To increase radiologic knowledge, the distribution of mammographic features on prior screening mammograms of missed interval and screen-detected cancers was compared to the distribution on diagnostic mammograms of screen-detected cancers. The same variables were compared on mammograms of discordant and concordant screen-detected cancers.

MATERIALS AND METHODS

The study was performed in Møre og Romsdal County, Norway, as a part of the quality assurance of the Norwegian Breast Cancer Screening Program. Women were screened using analog techniques and diagnosed from 2002 to 2008. Prior and diagnostic mammograms of 81 interval and 123 screen-detected breast cancers in women aged 50 to 71 years were retrospectively reviewed and classified as either missed or true by four experienced breast radiologists. Mammographic features were classified according to a modified Breast Imaging Reporting and Data System.

RESULTS

Thirty percent (24 of 81) of the interval cancers and 21% (26 of 123) of the screen-detected cancers were classified as missed. Calcifications, alone or in association with mass or asymmetry, tended to be more common on prior mammograms of missed cancers compared to diagnostic mammograms of screen-detected cancers (34% [17 of 50] vs 21% [26 of 123], P = .114), whereas an opposite trend was seen for mass (54% [27 of 50] vs 68% [84 of 123], P = .109). Similar results were seen when comparing discordant and concordant cancers.

CONCLUSIONS

Calcifications represent a challenge in the interpretation of screening mammograms. For educational purposes, the importance of reviewing both interval and screen-detected cancers is obvious. Knowledge gained from systematic reviews might reduce the number of missed cancers on mammographic screening. Performing reviews according to established guidelines would make it possible to compare results across screening programs.