Interval breast cancers in New South Wales, Australia, and comparisons with trials and other mammographic screening programmes

Ultrasound for Breast Cancer Screening in Resource-Limited Settings: Current Practice and Future Directions

Breast cancer (BC) is the most prevalent cancer among women globally. Cancer screening can reduce mortality and improve women's health. In developed countries, mammography (MAM) has been primarily utilized for population-based BC screening for several decades. However, it is usually unavailable in low-resource settings due to the lack of equipment, personnel, and time necessary to conduct and interpret the examinations. Ultrasound (US) with high detection sensitivity for women of younger ages and with dense breasts has become a supplement to MAM for breast examination. Some guidelines suggest using US as the primary screening tool in certain settings where MAM is unavailable and infeasible, but global recommendations have not yet reached a unanimous consensus. With the development of smart devices and artificial intelligence (AI) in medical imaging, clinical applications and preclinical studies have shown the potential of US combined with AI in BC screening. Nevertheless, there are few comprehensive reviews focused on the role of US in screening BC in underserved conditions, especially in technological, economical, and global perspectives. This work presents the benefits, limitations, advances, and future directions of BC screening with technology-assisted and resource-appropriate strategies, which may be helpful to implement screening initiatives in resource-limited countries.

Association of symptoms and interval breast cancers in the mammography-screening programme: population-based matched cohort study

Background

We assessed the association between symptoms reported at breast cancer screening visits and interval cancers (ICs) in a prospective manner.

Methods

This population-based matched cohort study uses data of the Finnish National Breast Cancer Screening Programme that invites women aged 50–69 years old during 1992–2012. Subjects who attended screening with symptoms were matched with asymptomatic reference cohorts based on age at screening visit, year of invitation, number of invited visits and municipality of invitation. The primary outcome was ICs.

Results

Women with a lump had a threefold (hazard ratio 3.7, 95% confidence interval (CI) 3.0–4.6) risk of ICs and a higher risk (hazard ratio 1.7, 95% CI 1.4 to 2.0) at the subsequent visit compared with those without a lump. The fatal interval cancer risk increased by 0.39 per 1000 screens with a lump. The cumulative incidences of interval cancer increased within a month of a mammography-negative visit with a lump and after about 6 months of the visit with retraction or nipple discharge.

Conclusion

Women with breast symptoms have a clearly increased risk of interval breast cancer after the screening visit. Our findings indicate the need for different screening strategies in symptomatic women.

Measuring the burden of interval cancers in long-standing screening mammography programmes

Objectives

Mammography screening programme sensitivity is evaluated by comparing the interval cancer rate (ICR) with the expected breast cancer incidence without screening, ie. the proportional interval cancer rate (PICR). The PICR is usually found by extrapolating pre-screening incidence rates, whereas ICR is calculated from data available in the screening programmes. As there is no consensus regarding estimation of background incidence, we seek to validate the ICR measure against the PICR.

Methods

Screening data from the three mammography screening programmes of Stockholm, Copenhagen, and Funen in the period 1989-2011 provided data to calculate the ICR. The most commonly described methods of extrapolating pre-screening incidence rates to calculate the PICR were illustrated and PICRs were calculated by year and programme using these different methods and compared with the ICRs.

Results

PICRs varied greatly, reaching a difference of 32–34% in Stockholm, 79% in Copenhagen, and 100–106% in Funen between the highest and the lowest value, depending on which method was applied. PICRs exhibited large variations yearly and from programme to programme. ICRs did not vary to the same extent, ranging on average from 0.100 to 0.136 in the first 12-months and between 0.201 and 0.225 in the last 12-months of the two-year period after a negative screen across the three programmes.

Conclusion

The value of the PICR is hugely influenced by which method is applied, whereas the ICR is calculated purely on data available within programmes. We find that the PICR, the establishing indicator for sensitivity, could preferably be replaced by the ICR.

Evaluation of the interval cancer rate and its determinants on the Girona Health Region's early breast cancer detection program

BACKGROUND

The main aim of this study is to estimate the rate of false negative and true IC on the Program for the Early Detection of Breast Cancer (PEDBC) run by the Girona Health Region (GHR) and compare the clinicopathological characteristics of these tumors with those detected within the same program.

METHODS

A retrospective cohort study including all women participating on the Girona PEDBC between 2000 and 2006, with negative mammography screening. The IC included are those detected between the first and second round of screening and between the second and third round.

RESULTS

We identified a total of 43 IC, representing an incidence rate of 0.70 cases per 1,000 screened women. Of the 43 probable IC, we were able to classify a total of 22 (51.2%) cases. Of these 22 cases, 54.5% were classified as true interval tumors, 13.6% false negatives, 18.2% occult tumors and the remaining 13.6% minimal sign.We found significant differences in some clinicopathological characteristics of the IC comparing with the tumors detected within the program during the same period.

CONCLUSIONS

The IC rate for the PEDBC is within the expected parameters, with a high proportion of cases of true interval cancers (54.5%) and a low proportion of false negatives (13.6%). The results show that the proportional incidence of IC is within the limits set by European Guidelines. Furthermore, it has been confirmed that IC display more aggressive clinicopathological characteristics than screening breast cancers.

A multiparametric serum marker panel as a complementary test to mammography for the diagnosis of node-negative early-stage breast cancer and DCIS in young women

BACKGROUND

The sensitivity of mammography for the detection of small lesions, including node-negative early-stage (T1N0) primary breast cancer (PBC) and ductal carcinoma in situ (DCIS), is significantly decreased in young patients. From a clinical standpoint, an inconclusive mammogram reflects the inability of clinicians to confidently decide whether patients should be referred for biopsy or for follow-up with repeat imaging.

METHODS

Specific ELISAs were developed for a panel of 13 well-recognized breast autoantigens (HSP60, FKBP52, PRDX2, PPIA, MUC1, GAL3, PAK2, P53, CCNB1, PHB2, RACK1, RUVBL1, and HER2). Circulating autoantibody levels were measured in a cohort of 396 serum samples from histologically confirmed DCIS (n = 87) or T1N0 PBC (n = 153) and healthy controls (n = 156).

RESULTS

Individually, antibodies against CCNB1, FKBP52, GAL3, PAK2, PRDX2, PPIA, P53, and MUC1 demonstrated discriminatory power between breast cancer and healthy control groups. At 90% sensitivity, the overall combined specificity of the autoantibody serum screening test was 42%. Adjustment for higher sensitivities of 95% and 99% resulted in 30% and 21% specificities, respectively (33% and 18% in T1N0 PBC and 28% and 21% in DCIS). Finally, in patients with node-negative early-stage breast cancer younger than 50 years, the autoantibody assay exhibited 59% specificity with a fixed sensitivity at 90%.

CONCLUSIONS

Our autoantibody panel allows accurate detection of early breast cancer and DCIS, notably in younger patients.

IMPACT

Clinical assessment of this autoantibody panel displays a potential to facilitate clinical management of early-stage breast cancer detection in cases of inconclusive mammogram.

Bodyweight and other correlates of symptom-detected breast cancers in a population offered screening

OBJECTIVE

To determine the factors associated with symptom-detected breast cancers in a population offered screening.

METHODS

We interviewed 1,459 Australian women aged 40-69, 946 with symptom-detected and 513 with mammogram-detected invasive breast cancers ≥ 1.1 cm in diameter about their personal, mammogram, and breast histories before diagnosis and reviewed medical records for tumor characteristics and mammogram dates, calculating ORs and 95% confidence intervals (CIs) for symptom- versus mammogram-detected cancers in logistic regression models.

RESULTS

Lack of regular mammograms (<2 mammograms in the 4.5 years before diagnosis) was the strongest correlate of symptom-detected breast cancer (OR = 3.04 for irregular or no mammograms). In women who had regular mammograms (≥ 2 mammograms in the 4.5 years before diagnosis), the independent correlates of symptom-detected cancers were low BMI (OR < 25 kg/m(2) vs. ≥ 30 kg/m(2) = 2.18, 95% CI 1.23-3.84; p = 0.008), increased breast density (available in 498 women) (OR highest quarter vs. lowest = 3.50, 95% CI 1.76-6.97; p (trend) = 0.004), high-grade cancer, and a larger cancer (each p < 0.01). In women who did not have regular mammograms, the independent correlates were age <50 years, a first cancer, and a ≥ 2-cm cancer. Smoking appeared to modify the association of symptom-detected cancer with low BMI (higher ORs for low BMI in current smokers) and estrogen receptor (ER) status (higher ORs for low BMI in ER cancers).

CONCLUSION

Women with low BMI may benefit from a tailored approach to breast cancer detection, particularly if they smoke.

Towards an optimal interval for prostate cancer screening

BACKGROUND

The rate of decrease in advanced cancers is an estimate for determining prostate cancer (PCa) screening program effectiveness.

OBJECTIVE

Assess the effectiveness of PCa screening programs using a 2- or 4-yr screening interval.

DESIGN, SETTING, AND PARTICIPANTS

Men aged 55-64 yr were participants at two centers of the European Randomized Study of Screening for Prostate Cancer: Gothenburg, Sweden (2-yr screening interval, n=4202), and Rotterdam, the Netherlands (4-yr screening interval, n=13 301). We followed participants until the date of PCa, the date of death, or the last follow-up at December 31, 2008, or up to a maximum of 12 yr after initial screening. Potentially life-threatening (advanced) cancer was defined as cancer with at least one of following characteristics: clinical stage ≥T3a, M1, or N1; serum prostate-specific antigen (PSA) >20.0 ng/ml; or Gleason score ≥8 at biopsy.

INTERVENTION

We compared the proportional total (advanced) cancer incidence (screen-detected and interval cases), defined as the ratio of the observed number of (advanced) cancers to the expected numbers of (advanced) cancers based on the control arm of the study.

MEASUREMENTS

The proportional cancer incidence from the second screening round until the end of observation was compared using a 2- or 4-yr screening interval.

RESULTS AND LIMITATIONS

From screening round 2 until the end of observation, the proportional cancer incidence was 3.64 in Gothenburg and 3.08 in Rotterdam (relative risk [RR]: 1.18; 95% confidence interval [CI], 1.04-1.33; p=0.009). The proportional advanced cancer incidence was 0.40 in Gothenburg and 0.69 in Rotterdam (RR: 0.57; 95% CI, 0.33-0.99; p=0.048); the RR for detection of low-risk PCa was 1.46 (95% CI, 1.25-1.71; p<0.001). This study was limited by the assumption that PSA testing in the control arm was similar in both centers.

CONCLUSIONS

A 2-yr screening interval significantly reduced the incidence of advanced PCa; however, the 2-yr interval increased the overall risk of being diagnosed with (low-risk) PCa compared with a 4-yr interval in men aged 55-64 yr. Individualized screening algorithms must be improved to provide the strategy for this issue.

A simple method to estimate the episode and programme sensitivity of breast cancer screening programmes

BACKGROUND

The estimation of breast cancer screening sensitivity is a major aim in the quality assessment of screening programmes. The proportional incidence method for the estimation of the sensitivity of breast cancer screening programmes is rarely used to estimate the underlying incidence rates.

METHODS

We present a method to estimate episode and programme sensitivity of screening programmes, based solely on cancers detected within screening cycles (excluding breast cancer cases at prevalent screening round) and on the number of incident cases in the total target population (steady state). The assumptions, strengths and limitations of the method are discussed. An example of calculation of episode and programme sensitivities is given, on the basis of the data from the IMPACT study, a large observational study of breast cancer screening programmes in Italy.

RESULTS

The programme sensitivity from the fifth year of screening onwards ranged between 41% and 48% of the total number of cases in the target population. At steady state episode sensitivity was 0.70, with a trend across age groups, with lowest values in women aged 50-54 years (0.52) and highest in those 65-69 (0.77).

CONCLUSIONS

The method is a very serviceable tool for estimating sensitivity in service screening programmes, and the results are comparable with those of other methods of estimation.

Complementary approaches to assessing risk factors for interval breast cancer

OBJECTIVE

To examine risk factors for interval breast cancer among women screened in a population-based mammography program.

METHODS

Risk for interval cancer was assessed in terms of both the incidence per 10,000 negative screens and the proportion of all breast cancers diagnosed among screened women. Interval (N = 557) and screen-detected cancers (N = 1,545) were identified among 208,667 women receiving mammography in Colorado (1994-2001). Logistic regression was used to assess independent effects of multiple factors.

RESULTS

Overall risk of interval cancer was 29.5/10,000 women screened. Incidence was higher in women >50 years (OR: 2.28, 1.86-2.80), with family history (OR: 2.23, 1.85-2.70), with dense breasts (OR: 3.84, 2.76-5.35), and using hormones (OR: 1.54, 1.20-1.97). Hispanics had lower incidence than Whites (OR: 0.52, 0.34-0.81). Interval cancers represented 26% of all cancers diagnosed. This proportion was higher in women <50 (OR: 1.41, 1.09-1.82) and in women with dense breasts (OR: 2.95, 1.94-4.48).

CONCLUSIONS

Incidence of interval cancer increases with age, breast density, hormone use, and family history. Attempts to reduce occurrence of these cancers through more sensitive and/or intensive screening should focus on these subgroups. The disproportionate number of interval cancers associated with young age and dense breasts suggests these cancers result from both rapid growth and difficulties in detection.

A pooled analysis of interval cancer rates in six European countries

The objective of this study was to assess detection rates and interval breast cancer (IC) rates from eight programmes in the European Breast Cancer Screening Network. A common data collection protocol was used to explore differences in IC rates among programmes and discuss their potential determinants. Pooled analysis was used to describe IC rates by age, compliance in screening, recall rate, screening detection (SD) rate and expected breast cancer incidence. Participation in screening averaged 77.9% (range 42.6-88.7%), recall rate 5.4% (range 3.3-17.7%) in the initial and 3.4% (range 1.8-8.9%) in the subsequent screening rounds, and SD rate was 60.4 (range 41.6-91) per 10 000 women in initial and 38.5 (range 31.3-62.6) in subsequent screens. IC rate during first 12 months after screening was 5.9 (range 2.1-7.3) per 10 000 women screened negative and 12.6 (range 6.3-15) in the second year of the interval. IC comprised 28% of the IC and SD cancers. The ratio between IC rate and expected incidence was 0.29 for the first 12 months and 0.63 for the 13-24 months period. Sensitivity was higher for the ages 60-69 years and for initial tests than subsequent tests. There were distinct differences in the IC rates between programmes. The results of this study reveal large variations in screening sensitivity and performance. Pooled evaluation of some process indicators within the European breast cancer screening programmes proved to be feasible and is likely to be useful for the future, particularly if it is performed regularly and extensively.

Reader practice in mammography screen reporting in Australia

Reader variability is a problem in mammography image reporting and compromises the efficacy of screening programmes. The purpose of this exploratory study was to survey reader practice in reporting screening mammograms in Australia to identify aspects of practice that warrant further investigation. Mammography reporting practice and influences on concentration and attention were investigated by using an original questionnaire distributed to screen readers in Australia. A response rate of 71% (83 out of 117) was achieved. Demographic data indicated that the majority of readers were over 46 years of age (73%), have been reporting on screening mammograms for over 10 years (61%), take less than 1 min to report upon a screening mammogram examination (66%), report up to 200 examinations in a single session (83%) and take up to 2 h to report one session (61%). A majority report on more than 5000 examinations annually (66%); 93% of participants regard their search strategy as systematic, 87% agreed that their concentration can vary throughout a session, 64% agreed that the relatively low number of positives can lead to lapses in concentration and attention and almost all (94%) participants agreed that methods to maximise concentration should be explored. Participants identified a range of influences on concentration within their working environment including volume of images reported in one session, image types and aspects of the physical environment. This study has provided important evidence of the need to investigate adverse influences on concentration during mammography screen reporting.

Screening histories of invasive breast cancers diagnosed 1989–2006 in the West Midlands, UK: variation with time and impact on 10-year survival

Objectives

To examine variations in screening status category with time for 20,862 invasive breast cancers diagnosed in the West Midlands between 1989 and 2006, and to provide 10-year relative survival rates for each category.

Method

Population-based breast screening was introduced in the West Midlands from 1988. Primary invasive breast cancers diagnosed from 1 April 1989 to 31 March 2006 in women eligible for breast screening were identified from the West Midlands Cancer Intelligence Unit's cancer registration database. A screening status was determined for each case using previously published methodology.

Results

Screening status rates are affected initially by the gradual rollout of the screening programme and more recently by the need to wait for three years before interval cancers and cancers in lapsed and non-attenders can be identified. In the steady-state period 1994–2003, 40.6% of invasive breast cancers were screen-detected, 36.3% were interval cancers and 11.2% were cancers in non-attenders (NA). Ten-year relative survival was 89.6% for screen-detected breast cancers, 73.3% for interval cancers and 51.9% for cancers in NA.

Conclusion

The detection of invasive breast cancers by screening has improved over time, with an equivalent reduction in the numbers of interval cancers. This, together with a stable rate of cancers in NA and an improvement in the survival of women with interval cancers, suggests that further improvements in breast cancer mortality can be predicted. International comparisons of interval cancer rates are difficult due to interprogramme differences in the time between screens.

Comparison of interval breast cancer rates for two-versus single-view screening mammography: a population-based study

OBJECTIVE

To determine whether the implementation of two-view mammography was followed by a reduction in the rates of interval cancers.

MATERIAL AND METHOD

We analyzed the data concerning women aged 50-69 who attended the breast cancer screening program between January 1, 1994 and December 31, 2006 in Isère, France. We performed Poisson regressions to estimate age-adjusted rate ratios of women being recalled, cancer detection, and interval cancer for two-view compared to single-view mammography.

RESULTS

After adjusting for age, two-view mammography was associated with a higher risk of cancer detection (1.37 [95% CI, 1.16-1.62]) and with a decreased risk of 12-month (0.46 [95% CI, 0.23-0.92]) and 24-month (0.64 [95% CI, 0.46-0.88]) interval cancer.

CONCLUSION

Two-view mammography for first and subsequent screens is associated with lower rates of interval breast cancer. This is at the expense of an increased number of women being recalled for further assessment after subsequent screens.

Breast cancer screening: emerging role of new imaging techniques as adjuncts to mammography

Early detection of breast cancer has been shown to reduce breast cancer deaths in randomised controlled trials (RCTs) of mammography in women aged 50-69 years, with weaker evidence of benefit in those aged 40-49 or 70 years and older. Magnetic resonance imaging (MRI) and ultrasonography have been evaluated in breast cancer screening, relative to, or in addition to, mammography, in selected populations; neither test has been examined in an RCT, and thus evidence of associated screening benefit is uncertain. MRI is more sensitive than mammography in screening women with suspected or proven inherited mutations of the breast cancer genes. The addition of MRI in screening this population detects 8-24 additional cancers per 1000 screens, but also significantly increases a woman's risk of being recalled for investigation or surgical biopsy for false-positive findings. In Australia, Medicare funding for MRI screening of women in specific risk groups was announced in February 2009. Ultrasonography can detect cancers not identified on mammography in asymptomatic women with dense breast tissue. Incremental ultrasound cancer detection is reported in 0.27%-0.46% of women with mammography-negative dense breasts; evidence varies on its association with false-positive findings. Computer-aided detection (CAD) is a complementary tool to mammography, prompting the reader to consider lesions on the mammogram that may represent cancer. Emerging evidence and improved CAD technology are likely to help define its role in breast screening.

Interval cancer incidence and episode sensitivity in the Norrbotten Mammography Screening Programme, Sweden

OBJECTIVES

To estimate the interval cancer incidence, its determinants and the episode sensitivity in the Norrbotten Mammography Screening Programme (NMSP).

SETTING

Since 1989, women aged 40-74 years (n = 55,000) have been invited to biennial screening by the NMSP, Norrbotten county, Sweden.

METHODS

Data on 1047 invasive breast cancers from six screening rounds of the NMSP (1989-2002) were collected. We estimated the invasive interval cancer rates, rate ratios and the episode sensitivity using the detection and incidence methods. A linear Poisson-model was used to analyse association between interval cancer incidence and sensitivity.

RESULTS

768 screen-detected and 279 interval cancer cases were identified. The rate ratio of interval cancer decreased with age. The 50-59 year age group showed the highest rate ratio (RR = 0.52, 95% CI 0.41-0.65) and the 70-74 year age group the lowest (RR = 0.23, 95% CI 0.15-0.36). The rate ratios for the early (0-12 months) and late (13-24 months) interval cancers were similar (RR = 0.18, 95% CI 0.15-0.22 and 0.20, 95% CI 0.17-0.24). There was a significantly lower interval cancer incidence in the prevalence round as compared with the incidence rounds. According to the detection method the episode sensitivity increased with age from 57% in the age group 40-49 years to 84% in the age group 70-74 years. The corresponding figures for the incidence method were 50% and 77%, respectively.

CONCLUSION

Our study showed an interval cancer incidence of 38% and the episode sensitivity of 62-73%, depending on the method of calculation. Our results are of clinically acceptable level and concert with the reference values of the European guidelines.

Quality of mammography screening in the Milan programme: evidence of improved sensitivity based on interval cancer proportional incidence and radiological review

BACKGROUND

Interval cancer (IC) incidence and review-based initial evaluation of Milan service screening (ASLMI1) suggested suboptimal performance. We report results in a subsequent screening round to further determine screening quality.

METHODS

IC was identified in subjects with a negative screening episode in 2005 (N=33,258) by linkage with 2005-2007 Hospital Discharge Records. IC proportional incidence-based sensitivity was estimated. Radiological review, with case-mix, was conducted in a blinded manner. Linkage and review modalities were maintained as for initial evaluation.

RESULTS

30 identified IC accounted for 6.99% (year 1), 27.84% (year 2), and overall 17.44% (2-year screening interval) proportional incidence. Estimated sensitivity was 93.01% (year 1), 72.16% (year 2) and 82.55% (2-year interval). Review classified 5 (16.6%) as screening error, 2 (6.7%) as minimal signs, and 23 (76.7%) as occult.

CONCLUSION

Programme sensitivity is now within recommended European standards. Performance indicators improved relative to initial evaluation. Both increasing experience and formal training of radiologists are likely to have contributed to this improvement.

Interval breast cancers in a community screening programme: frequency, radiological classification and prognostic factors

The frequency of interval cancers (IC) can be an indicator inversely related to the quality of a breast screening programme. The objectives were to estimate the frequency of IC, to classify IC by posterior radiological review, and to describe the prognostic factors of these IC. The setting was the Sabadell-Cerdanyola Breast Cancer Screening Programme, in Northeast Spain. We developed a population-based study of the IC occurring in the first three rounds (1995-2001). The indicators used were the incidence rate of invasive IC per 10 000 women screened and the proportional incidence, stratified by age group, type of screening and the round, and the time elapsed since the last screening mammogram. A radiological informed consensus review was used to classify the IC. No specific pattern of incidence rates was evident with respect to age, type of screening, or round, although screening was generally more sensitive in women aged 60-69 years. The proportional incidence for the period 0-11 months was always under 30%. Twenty-one percent of 38 IC evaluated (95% CI: 8.0-34.0) were attributed to errors in the screening process (false negatives). No major differences in the prognostic factors of the 57 IC were identified on examining the radiological type or the time since the last screening mammogram. We observed a high frequency of IC from 12 months after screening. It is necessary to reach a consensus regarding the definition and the analysis of IC and to establish mechanisms that would allow all the malignant tumours diagnosed in the target population to be identified.

Incidence of interval breast cancers after 650,000 negative mammographies in 13 Italian health districts

OBJECTIVES

To estimate the total proportional incidence of interval breast cancers in a two-yearly mammography screening programme, and to perform subgroup analyses by woman's age, screening centre-specific recall rate and screening round.

METHODS

Using unconverted electronic data-sets from the 13 screening centres in the Emilia-Romagna Region of northern Italy (540,450 women aged 50-69 years), a database of 919,538 mammography records was created. Of these, 655,175 eligible single-mammography records (1997-2002) from 379,318 women were record-linked with the regional Breast Cancer Registry. In the two-year inter-screening interval, a total of 1,022,694.3 woman-years at risk were accumulated, with 695 interval cancers observed and 2428.3 expected. The observed number of interval cancers was divided by the expected number to obtain the proportional incidence.

RESULTS

The total proportional incidence of first- and second-year interval cancers was 0.18 (95% CI 0.15-0.20) and 0.43 (0.39-0.47), respectively. Woman's age was inversely associated with proportional incidence in both interval years, with a cut-off point at age 60. A screening centre-specific recall rate greater than the regional average of 5% was associated with a proportional incidence of 0.14 (0.11-0.17) versus 0.20 (0.17-0.24) in the first interval year, and of 0.36 (0.31-0.41) versus 0.50 (0.44-0.56) in the second. The proportional incidence remained unchanged between the first and subsequent screening rounds.

CONCLUSIONS

The results were in line with the previous Italian data and with the recommended European standards. The inverse effect of woman's age and of recall rate was expected.

Interval cancers in the beginning years of the breast cancer screening programme in the Belgian province of Limburg

OBJECTIVE

To assess the occurrence of interval breast cancers among those women who attended the mammography screening programme in the Belgian province of Limburg. Interval cancers are tumours that are being diagnosed before the next scheduled screening round and are related to the sensitivity and the screening interval.

METHODS

Biennial screening is provided to all women aged 50-69. The records of the screening programme were linked to those of the cancer registry. The interval cancer rate, expressed as a proportion of the underlying (expected) breast cancer incidence rate was calculated. The observed interval cancer incidence is the number of interval cancers per 10,000 'negative' screening tests.

RESULTS

The interval cancer rate in the first year was 25.37% for all cancers (ductal carcinoma in situ included) and 21.7% when the analysis was restricted to invasive tumours. Proportional incidence of interval cancer in the second year after screening was 12.02% for all cancers.

CONCLUSION

In conclusion, the interval cancer rates in the Belgian province of Limburg were compatible with the European guidelines. However, increasing the recall rate in our programme and systematically reviewing the interval cancers may improve the quality of the programme even further.

Evaluating Population-Based Screening Mammography Programs Internationally

This report describes the purpose and activities of the International Breast Cancer Screening Network (IBSN), a voluntary consortium of countries that focuses on collaborative research to identify and promote efficient, effective approaches to breast cancer control world-wide through population-based screening mammography. Sponsored by the U.S. National Cancer Institute, the IBSN was established in 1988 with eleven participating countries. By 2005, membership had grown to 27 countries. Recent IBSN efforts have involved gathering information on program organization and quality assurance activities, evaluating measures and methodologies for assessing screening mammography performance and outcomes, and examining the information that programs are providing to women as a means of facilitating informed decision-making about the benefits and risks of screening mammography. The ongoing IBSN effort demonstrates that-despite marked differences in health care systems-international collaborative work can contribute new knowledge to the monitoring and evaluation of organized, population-based screening mammography programs, and identify potential areas for improvement in screening performance in practice.

Radiological surveillance of interval breast cancers in screening programmes

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.

Methodological issues in international comparison of interval breast cancers

International comparisons of interval cancers (IC) are important to better understand the relationship between programmes' performance and screening practices. In this respect, differences in (i) definition, (ii) identification and (iii) quantification of IC have received little attention. To examine these 3 comparability issues and activities involving IC, an assessment was conducted among member countries of the International Breast Cancer Screening Network, and the impact of accuracy of identification and quantification practices was estimated using 1996-98 data from the Dutch breast cancer screening programme. Information was obtained from 19 screening programmes in 18 countries, 16 of which acknowledged the coexistence of opportunistic screening. IC data were collected to evaluate performance of the screening programme (100% of programmes) and the radiologists (89%); 53% of programmes had a designated review process for IC. Most programmes (84%) agreed with the European Guidelines definition of IC, but a case situation exercise evidenced substantial discrepancy in classification of cancers that occurred after a positive screen. Completeness of identification of IC appears to contribute most to international variation, and cannot be easily controlled for in methodologically rigorous comparisons. Statistically significant differences of about 4% were measured between quantification methods for IC. An operational definition of IC is proposed to enhance international comparability. Valid comparisons of IC are possible with careful attention to the definition but true differences in IC frequency across screening programmes should exceed 10% to be possibly indicative of real differences between programmes.

Episode sensitivity in association with process indicators in the Finnish breast cancer screening program

We assessed the episode sensitivity of the Finnish mammography program for women aged 50-59 (partly 60-64) years and explored associations between the episode sensitivity and the screening process indicators from 1991 to 1999. For the study period, data were available from 10 screening centers. Records of 721,000 screening visits were linked to the files of the nationwide Finnish Cancer Registry from 1991 to 2001 at an individual level. The rates of screen-detected and interval breast cancers were calculated at the first and at the subsequent screens. The episode sensitivity was determined by contrasting the incidence of interval cancers with the expected population incidence rate without screening (incidence method) and as a proportion of interval cancers out of all cancers detected (detection method). At the subsequent screens, the episode sensitivity determined by the incidence method was 54% and by the detection method 65%. The sensitivity 0-11 and 12-23 months after the screening was 70% and 38%, respectively. The episode sensitivity decreased toward the end of the study period and increased with age. The center-specific sensitivity increased 13% per 1% absolute increase in the recall rate. In general, our study provides further information on the effectiveness of screening programs. The sensitivity estimates were comparable with those from other European service screening programs. The variability in the episode sensitivity suggests potential for variations in the future screening outcome.

Reporting of performance indicators of mammography screening in Europe

We compared short-term indicators for service mammography screening in Europe. Data were available from 17 programmes, although not all programmes provided a comprehensive reporting. More than 90% of the target population had been screened within the last 3 years in the WE trial, whereas only two-thirds of women in England and Copenhagen had been screened within the last 3 years, which will delay or reduce the effect of screening compared with the trial. Participation was highest in sparsely populated areas. Detection rates at first screen reached three times the baseline in Copenhagen, the Netherlands and North-West England. The clinical characteristics of screen-detected cases were badly reported. Given their importance for the long-term effect of screening, further data are warranted. Sensitivity and specificity could be measured only indirectly; they showed, however, considerable variation between programmes. Fyn, Florence and Stockholm had succeeded in combining high specificity with high sensitivity. With different recall policies, different proportions of women will experience a false-positive test; expected numbers after three screens were 14%, 10% and 1%, for England, Copenhagen and the Netherlands, respectively. Based on the observed wide variation in short-term indicators, a similar wide variation is expected in the effect of screening on breast cancer mortality.