Clinical Image Quality and Sensitivity in an Organized Mammography Screening Program

PURPOSE

The study sought to examine the association between clinical image quality of mammograms and screening sensitivity.

METHODS

Four radiologists evaluated the clinical image quality of 374 invasive screen-detected cancers and 356 invasive interval breast cancers for which quality evaluation of screening mammograms could be assessed from cancers diagnosed among participants in the Quebec Breast Cancer Screening Program in 2007. Quality evaluation was based on the Canadian Association of Radiologists accreditation criteria, which are similar to those of the American College of Radiology. The association between clinical quality and screening sensitivity was assessed by logistic regression. Adjusted sensitivity and adjusted sensitivity ratios were obtained through marginal standardization. No institutional review board approval was required.

RESULTS

A proportion of 28% (206 of 730) of screening mammograms had lower overall quality for the majority of assessments. Positioning was the quality attribute that was the most frequently deficient. The 2-year screening sensitivity reached 68%. Sensitivity of screening was not statistically associated with the overall quality (ratio of 2-year sensitivity = 1.03; 95% confidence interval: 0.93-1.15) or with any quality attributes (positioning, exposure, compression, sharpness, artifacts, contrast). Results were similar for the 1-year sensitivity.

CONCLUSIONS

Although not all mammograms in the Quebec screening program met the optimum quality required by the Canadian Association of Radiologists or American College of Radiology accreditation, the screening mammograms produced in this population-based organized screening program reached a high enough level of quality so that the remaining variation in quality is too little to impair screening sensitivity.

Digital Compared with Screen-Film Mammography: Measures of Diagnostic Accuracy among Women Screened in the Ontario Breast Screening Program

PURPOSE

To compare measures of diagnostic accuracy between large concurrent cohorts of women screened with digital computed radiography (CR), direct radiography (DR), and screen-film mammography (SFM).

MATERIALS AND METHODS

This study was approved by the University of Toronto Research Ethics Board; informed consent was not required. Three concurrent cohorts of women aged 50-74 years who were screened from 2008-2009 in the Ontario Breast Screening Program with SFM (487,334 screening examinations, 403,688 women), DR (254,758 screening examinations, 220,520 women), or CR (74,140 screening examinations, 64,210 women) were followed for 2 years or until breast cancer diagnosis. Breast cancers were classified as screening-detected or interval on the basis of the woman's final screening and assessment results. Interval cancer rate (per 10 000 negative screening examinations), sensitivity, and specificity were compared across the cohorts by using mixed-effects logistic regression analysis.

RESULTS

Interval cancer rates were higher, although not significantly so, for CR (15.2 per 10,000; 95% confidence interval [CI]: 12.8, 17.8) and were similar for DR (13.7 per 10,000; 95% CI: 12.4, 15.0) compared with SFM (13.0 per 10,000; 95% CI: 12.1, 13.9). For CR versus SFM, specificity was similar while sensitivity was significantly lower (odds ratio [OR] = 0.62; 95% CI: 0.47, 0.83; P = .001), particularly for invasive cancers detected at a rescreening examination, for women with breast density of less than 75%, for women with no family history, and for postmenopausal women. For DR versus SFM, sensitivity was similar while specificity was lower (OR = 0.92; 95% CI: 0.87, 0.98; P = .01), particularly for rescreening examinations, for women aged 60-74 years, for women with breast density of less than 75%, for women with a family history, and for women who were postmenopausal.

CONCLUSION

Given the 38% lower sensitivity of CR imaging systems compared with SFM, programs should assess the continued use of this technology for breast screening.

Abstract P3-02-10: Implementation and uptake of a provincial, population-based, organized breast screening program for high risk women in Ontario: The Ontario breast screening program (OBSP) high risk program

Background: Genetic testing for mutations in BRCA1/2 has been clinically available in Ontario since 2000. Over 15000 individuals have been tested. Evidence from clinical trials has consistently shown that women at high risk of breast cancer (BrCa) benefit from BrCa screening that includes both magnetic resonance imaging (MRI) of the breast and mammography, yet access to MRI in Ontario was variable. In 2011, Cancer Care Ontario (CCO) established an expert panel to develop a protocol for expanding the OBSP, initially created for average risk women 50–74, to include MRI and mammography for eligible high risk women.

Methods: The panel's tasks included: 1. determining high risk criteria 2. estimating the prevalence of high risk women 3. selecting a cancer risk model 4. developing a referral and assessment pathway for potentially eligible subjects 5. developing educational resources, training plan and communication strategy for relevant stakeholders 6. developing indicators for program evaluation, 7. providing guidance for post-implementation issues.

Results: The program was initiated July, 2011 and now includes 28 sites. Women aged 30–69 with and without a history of breast cancer are eligible if they 1. are BRCA1/2 mutation carriers or untested first degree relatives of carriers, 2. have a lifetime risk of breast cancer >=25% based on family history according to IBIS or BOADICEA risk models, or 3. received prior radiation therapy to the chest. It is estimated that 34000 high risk women in the target age group live in Ontario. Preliminary volume data for the first 9 mos are shown in Table 1. Of the 5037 women participating, 802 have been referred directly by their physician and 4,235 have been referred for genetic assessment. Of the 2,946 women who received genetic assessment, 31% met the high risk criteria. To date, 729 high risk MRI scans have been performed.

Conclusions: A population based organized screening program for high risk women that includes genetic risk assessment has been implemented in Ontario. Further evaluation of risk assessment and screen results are underway. To our knowledge, this is the first organized screening program for women at high risk of breast cancer.

Implementation of a population-based breast screening program for high-risk women in Ontario: The Ontario Breast Screening Program (OBSP) High-Risk Program

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Background: Genetic testing for mutations in BRCA1 and BRCA2 has been clinically available in Ontario since 2000. It is estimated that over 15000 individuals have been tested. Evidence from clinical trials have consistently shown that women at high risk of breast cancer such as BRCA1/2 mutation carriers benefit from breast cancer screening that includes both magnetic resonance imaging (MRI) of the breast and mammography, yet access to MRI in Ontario was variable. In 2011, Cancer Care Ontario established an expert panel to develop a protocol for expanding the Ontario Breast Screening Program, initially created for average risk women 50-74, to include MRI and mammography for eligible high risk women. Methods: The panel’s tasks included: 1. determining the criteria for high risk, 2. estimating the prevalence of high risk women, 3. selecting a model to estimate cancer risk, 4. developing a referral and assessment pathway for potentially eligible subjects to receive genetic counseling/risk assessment and screening if eligible, 5. developing educational resources, training plan and communication strategy for relevant stakeholders including primary care providers, oncologists, geneticists and genetic counselors, 6. developing indicators to permit program evaluation, 7. providing guidance for post-implementation issues such as subject eligibility and interpretation of genetic test results. Results: The program was initiated July, 2011 at 19 sites. Women aged 30-69 with and without a history of breast cancer are eligible if they 1. are BRCA1/2 mutation carriers or untested first degree relatives of carriers, 2. have a lifetime risk of breast cancer >=25% based on family history, or 3. received prior radiation therapy to the chest. It is estimated that 34000 high risk women in the target age group live in Ontario. Conclusions: A population based organized screening program for high risk women that includes genetic risk assessment has been implemented in Ontario. To our knowledge, this is the first organized screening program for women at high risk of breast cancer.

Long-term results of screening with magnetic resonance imaging in women with BRCA mutations

Background:

The addition of breast magnetic resonance imaging (MRI) to screening mammography for women with BRCA mutations significantly increases sensitivity, but there is little data on clinical outcomes. We report screening performance, cancer stage, distant recurrence rate, and breast cancer-specific mortality in our screening study.

Methods:

From 1997 to 2009, 496 women aged 25 to 65 years with a known BRCA1/2 mutation, of whom 380 had no previous cancer history, were enrolled in a prospective screening trial that included annual MRI and mammography.

Results:

In 1847 screening rounds, 57 cancers were identified (53 screen-detected, 1 interval, and 3 incidental at prophylactic mastectomy), of which 37 (65%) were invasive. Sensitivity of MRI vs mammography was 86% vs 19% over the entire study period (P<0.0001), but was 74% vs 35% from 1997 to 2002 (P=0.02) and 94% vs 9% from 2003 to 2009 (P<0.0001), respectively. The relative sensitivities of MRI and mammography did not differ by mutation, age, or invasive vs non-invasive disease. Of the incident cancers, 97% were Stage 0 or 1. Of 28 previously unaffected women diagnosed with invasive cancer, 1 BRCA1 mutation carrier died following relapse of a 3 cm, node-positive breast cancer diagnosed on her first screen at age 48 (annual breast cancer mortality rate=0.5%). Three patients died of other causes. None of the 24 survivors has had a distant recurrence at a median follow-up of 8.4 years since diagnosis.

Conclusion:

Magnetic resonance imaging surveillance of women with BRCA1/2 mutations will detect the majority of breast cancers at a very early stage. The absence of distant recurrences of incident cancers to date is encouraging. However, longer follow-up is needed to confirm the safety of breast surveillance.

Recording of hormone therapy and breast density in breast screening programs: summary and recommendations of the International Cancer Screening Network

Breast density and the use of hormone therapy (HT) for menopausal symptoms alter the risk of breast cancer and both factors influence screening mammography performance. The International Cancer Screening Network (ICSN) surveyed its 29 member countries and found that few programs record breast density or the use of HT among screening participants. This may affect the ability of programs to assess their effectiveness in reducing breast cancer mortality. Seven countries recorded the use of HT at screening, and some were able to link screening records to individual prescribing records of HT. Eight countries reported recording breast density at screening mammography for some or all women screened. The recommendations of the ICSN for recording information about breast density and HT are presented.

Systematic review: using magnetic resonance imaging to screen women at high risk for breast cancer

BACKGROUND

A sensitive and acceptable screening regimen for women at high risk for breast cancer is essential. Contrast-enhanced magnetic resonance imaging (MRI) of the breast is highly sensitive for diagnosis of breast cancer but has variable specificity.

PURPOSE

To summarize the sensitivity, specificity, likelihood ratios, and posttest probability associated with adding MRI to annual mammography screening of women at very high risk for breast cancer.

DATA SOURCES

English-language literature search of the MEDLINE, EMBASE, and Cochrane databases from January 1995 to September 2007, supplemented by hand searches of pertinent articles.

STUDY SELECTION

Prospective studies published after 1994 in which MRI and mammography (with or without additional tests) were used to screen women at very high risk for breast cancer.

DATA EXTRACTION

Methods and potential biases of studies were assessed by 2 reviewers, and data were extracted and entered into 2 x 2 tables that compared American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) scores of MRI plus mammography, mammography alone, or MRI alone with results of breast tissue biopsies.

DATA SYNTHESIS

Eleven relevant, prospective, nonrandomized studies that ranged from small single-center studies with only 1 round of patient screening to large multicenter studies with repeated rounds of annual screening were identified. Characteristics of women that varied across study samples included age range, history of breast cancer, and BRCA1 or BRCA2 mutation status. Studies used dynamic contrast-enhanced MRI with axial or coronal plane images (European studies) or sagittal images (North American studies) that were usually interpreted without knowledge of mammography results. The summary negative likelihood ratio and the probability of a BI-RADS-suspicious lesion (given negative test findings and assuming a 2% pretest probability of disease) were 0.70 (95% CI, 0.59 to 0.82) and 1.4% (CI, 1.2% to 1.6%) for mammography alone and 0.14 (CI, 0.05 to 0.42) and 0.3% (CI, 0.1% to 0.8%) for the combination of MRI plus mammography, using a BI-RADS score of 4 or higher as the definition of positive.

LIMITATIONS

Differences in patient population, center experience, and criteria for positive screening results led to between-study heterogeneity. Data on patients with nonfamilial high risk were limited, and no data were available on recurrence or survival.

CONCLUSION

Screening with both MRI and mammography might rule out cancerous lesions better than mammography alone in women who are known or likely to have an inherited predisposition to breast cancer.

Outcomes of surveillance mammography after treatment of primary breast cancer: a population-based case series

GOAL

To ascertain outcomes of surveillance mammography (SM) following treatment of early stage unilateral primary breast cancer (PBC) in a population based case series.

METHODS

Random samples from all 12,279 women having breast surgery within 4 months after diagnosis of PBC, between July 1991 and December 1993 in Ontario, were drawn from a database created by deterministic linkage of PBC files from the Ontario Cancer Registry (OCR) with episodes of breast surgery extracted from the hospital Discharge Abstract Database (DAD), and mammography from the Ontario physician billings database (OHIP). Among women having >or=1 episode(s) of breast surgery subsequent (SBS) to the date of diagnosis up to December 2000, a sample of 1,200/5,064 (23.7%) was drawn, and among women with no SBS, a sample of 400/7,215 (5.5%). Among these two samples, operative, pathology, and mammography reports were abstracted from original charts. Treatments were abstracted and categorized. Women with complete data for Stages 1 and 2 unilateral PBC were included. From the subsequent surgery sample, 609/1,200 (50.8%) were excluded because of simultaneous or sequential bilateral breast cancers or mastectomies within 6 months, missing stage information, Stage 3 or 4 PBC, or missing primary charts. From the no subsequent surgery sample, 90/400 (22.5%) were excluded by the same criteria. Episodes of bilateral 2-view X-ray mammography, beginning >or=6 months after the diagnosis of unilateral PBC, and if multiple, at least 11 months apart, and not prompted by a clinical concern or symptom, were classified as SM. We confirmed episodes of cancer recurrence within the ipsilateral conserved breast (CRICB) and metachronous contralateral primary breast cancer (CPBC) >or=6 months after the diagnosis of the unilateral PBC from original operative and pathology reports. We used Cox models to describe the association of exposure to >or=1 episode(s) of SM with the risk of death from breast cancer among the study population, and separately among women experiencing CRICB or CPBC.

RESULTS

Eligible women comprising 591/1,200 and 310/400 produced a combined case series of 901/1,600 (56.3%). Women with >or=1 episode(s) of SM numbered 721/901 (80.0%). We confirmed 84 CRICB events among 584 women initially treated by lumpectomy (14.4%), and 49 CPBC events among all 901 women in the study population (5.4%). Among women having >or=1 episode(s), the 25th percentile of observed follow up was 1,631 days, the 50th, 4,287 days, and the 75th 5,011 days. Among women without any SM, the 25th percentile of observed follow-up was 440 days, the 50th, 891 days, and the 75th, 1,849 days. Hazard ratio (HR) for death due to breast cancer associated with >or=1 episode of SM was 0.28 (95% CI 0.22-0.37), adjusted for age, stage, type of surgery, adjuvant chemotherapy, and tamoxifen. Among 84/584 women with CRICB, unadjusted HR = 0.36 (95%CI 0.13, 1.00) and among 49/901 women with CPBC, unadjusted HR = 0.86 (0.20-3.77).

CONCLUSION

SM was associated with a significant reduction in the hazard for breast cancer death. Among women who experienced CRICB, the reduction was of borderline significance, and the reduction was not significant among women who experienced CPBC.

Influence of Patterns of Hormone Replacement Therapy Use and Mammographic Density on Breast Cancer Detection

BACKGROUND

There is evidence that factors such as current hormone replacement therapy (HRT) use and mammographic density may each lower the sensitivity of mammography and are associated with a greater risk of developing an interval cancer. This study explores this relationship further by examining the influence of patterns of HRT use and the percentage of mammographic density on the detection of breast cancer by classification of interval cancer.

METHODS

This study uses a case-case design nested within a cohort of women screened by the Ontario Breast Screening Program between 1994 and 2002. Interval cancers, both those missed at screening but seen on retrospective review (n = 87) or true intervals without visible tumor signs at screening (n = 288) were matched to 450 screen-detected cancers. The association between the percentage of mammographic density, measured by radiologists and a computer-assisted method, and HRT use, ascertained from a mailed questionnaire, and the risk of being diagnosed with an interval cancer was estimated using conditional logistic regression.

RESULTS

A monotonic gradient of increasing risk for interval cancers was found for each 25% increase in mammographic density [odds ratio (OR), 1.77; 95% confidence intervals (95% CI), 1.07-2.95 for missed intervals and OR, 2.16; 95% CI, 1.59-2.94 for true intervals]. After adjusting for mammographic density, a significantly increased risk for true-interval cancers remained for women taking estrogen alone (OR, 1.75; 95% CI, 1.11-2.83) as well as for missed- (OR, 2.84; 95% CI, 1.32-6.13) and true-interval cancers (OR, 1.79; 95% CI, 1.10-2.90) for women taking combined HRT.

CONCLUSIONS

Information on mammographic density and HRT use should routinely be collected at the time of screening. Women at risk should be made aware of the lower sensitivity of mammography and offered alternative procedures for screening.

Performance measures from 10 years of breast screening in the Ontario Breast Screening Program, 1990/91 to 2000

Performance measures for the Ontario Breast Screening Program (OBSP) by age group, time period and screening modality from 10 years of breast screening were evaluated. Data were available from routine information collected on 283,962 women aged 50 to 69 screened at 73 screening centres between 1 July 1990 and 31 December 2000. Although, initially, participation in the OBSP was low, this rate increased over time and the majority of women screened returned for subsequent screening. Abnormal call rates increased slightly over the time period, were higher in women aged 50 to 59, and for women with mammographic abnormalities. Detection rates of invasive cancer were higher and prognostic features of cancers were better for women age 60 to 69, and those referred by mammography. Along with the prognostic features of cancers, the benign to malignant surgical ratio and diagnostic interval improved over the time periods and for women aged 60 to 69. Greater proportions of women had shorter diagnostic intervals and were more likely to have a diagnosis of breast cancer after surgery if they were referred by both clinical breast examination and mammography. Although some enhancements of the programme are necessary, the OBSP met or exceeded Canadian targets for most performance measures.

Organized breast screening programs in Canada: effect of radiologist reading volumes on outcomes

PURPOSE

To examine retrospectively the relationship between radiologist screening program reading volumes and interpretation results.

MATERIALS AND METHODS

This research project was reviewed by the University of British Columbia Research Ethics Board. Informed patient consent was not required. Data were requested from Canadian provincial screening programs for the period 1988-2000. Cancer detection rates, abnormal interpretation rates, and positive predictive values (PPVs) were calculated for individual radiologists in those programs. Multivariate Poisson mixed regression models were used to examine the effect of patient age, screening examination sequence (first or subsequent screening examination), province, radiologist reading volume, and interradiologist differences on cancer detection rate, abnormal interpretation rate, and PPV.

RESULTS

The results of the interpretation of 1406678 screening mammograms by 304 radiologists from seven provincial programs were analyzed. Cancer detection rate, abnormal interpretation rate, and PPV all varied according to age of woman screened and screening sequence and across the sample of radiologists. None of the rates varied by province. Neither the cancer detection rate nor the abnormal interpretation rate varied by reading volume, but the average PPV was increased by 34% for volumes over 2000 mammograms versus volumes of 480-699 mammograms per year. There was no evidence that the magnitude of variability around the average, for radiologists reading the same volume of mammograms, varied across different volume groups for any of the outcome measures.

CONCLUSION

Cancer detection did not vary with reading volume. The average PPV for individual radiologists increased as reading volume rose up to 2000 mammograms per year; it stabilized at higher volumes.

A hybrid breast biopsy system combining ultrasound and MRI

System design and initial phantom accuracy results for a novel biopsy system integrating both magnetic resonance (MR) and ultrasound (US) imaging modalities are presented. A phantom experiment was performed to investigate the efficacy of this hybrid guidance biopsy technique in a breast tissue mimicking phantom. A comparison between MR-guided core biopsy verses MR/US-guided core biopsy of phantom targets was realized using a scoring system based on the consistency of the acquired core samples (14 gauge). It was determined that the addition of US to guide needle placement improved the accuracy from an average score of 7.4 out of 10 (MRI guidance alone), to 9.6 (MRI/US guidance) over 21 trials. The average amount of needle tip correction resulting from the additional US information was determined to be 3.7 mm. This correction value is substantial, equal to approximately one radius of the intended targets. Hybrid US/MRI guided biopsy appears to offer a simple means to ensure accurate breast tissue sampling without the need for repeat MRI scans for verification or the need for real-time imaging in open MRI geometries.

Influence of delay to diagnosis on prognostic indicators of screen-detected breast carcinoma

BACKGROUND

Although delay to diagnosis after a breast screening abnormality causes anxiety, its effect on prognosis is unknown.

METHODS

Using pooled data from five Canadian organized breast cancer screening programs, the authors used unconditional logistic regression to evaluate the effect of delay to diagnosis on prognostic indicators among 4465 women with invasive breast carcinoma diagnosed in the ipsilateral breast within 3 years of an abnormal screen performed during 1990-1996.

RESULTS

Women with high-suspicion screens (n = 1569) compared with those without (n = 2896) were more promptly investigated (median days from screen to diagnosis, 31 vs. 47; P < or = 0.0001), had larger tumors (79.4% vs. 55.9% > 10 mm; P < or = 0.0001), and were more likely to be lymph node positive (33.9% vs. 17.3%; P < or = 0.0001). For delays beyond > 12 to < or = 20 weeks, a linear trend of increased tumor size and lymph node positivity began to emerge. Controlling for suspicion, the authors found that odds ratios for tumor size greater than 10 mm were 0.9 (95% CI, 0.66-1.17), 1.2 (95% confidence interval [CI], 0.88-1.56), 1.5 (95% CI, 1.05-2.16), and 2.1 (95% CI, 1.15-3.86) for delays of > 12 to < or = 20, > 20 to < or = 52, > 52 to < or = 104, and > 104 < or = 156 weeks, respectively (p(trend) < or = 0.0001), compared with delays of > 4 to < or = 12 weeks. Similarly, odds ratios for lymph node metastasis were 1.0 (95% CI, 0.67-1.42), 1.2 (95% CI, 0.84-1.69), 2.2 (95% CI, 1.48-3.15), and 3.2 (95% CI, 1.84-5.55) for the same time intervals (p(trend) = 0.0033).

CONCLUSIONS

The authors' findings suggest that delays to diagnosis of asymptomatic breast carcinoma of 6 to 12 months are associated with progression of breast carcinoma as measured by increasing risk of lymph node metastases and larger tumor size. A policy of early recall rather than biopsy for low suspicion mammographic abnormalities may introduce delays of this magnitude. The tendency to more expediently investigate women with high-suspicion, worse prognosis screens (suspicion bias) obscures whether delays shorter than 20 weeks also worsen prognostic indicators. Suspicion bias should be considered when interpreting the effect of delay on prognosis.

Stromal fibrosis of the breast

OBJECTIVE

The purpose of this retrospective study was to describe the imaging features of stromal fibrosis of the breast and to determine the false-negative rate (number of cancers missed) at percutaneous biopsy.

MATERIALS AND METHODS

Between January 1997 and October 1999, 1095 imaging-guided core biopsies were performed. Patients were included in our study if stromal fibrosis was the predominant histologic finding. Cores adjacent to previous excisional biopsies or from calcified lesions were excluded.

RESULTS

Stromal fibrosis was diagnosed in 74 (6.8%) of 1095 imaging-guided core needle biopsies in 73 patients. The 10 mammographic lesions were variable in appearance. Most of the sonographic lesions were indeterminate, with 16 (25%) of 64 showing suspicious features. Discordant imaging resulted in three patients having a second core biopsy and nine patients having an excisional biopsy. The two false-negative findings were the result of an infiltrating lobular carcinoma and an infiltrating ductal carcinoma, the latter diagnosis delayed for 6 months.

CONCLUSION

The low incidence (2.7%) of missed cancers in our series suggests that patients diagnosed at core biopsy as having stromal fibrosis can be treated conservatively with a short-term follow-up protocol. However, it would be prudent to continue to recommend either a second core biopsy or an excisional biopsy for imaging features that cannot be reliably differentiated from malignancy.

Role of equalisation mammography of dense breasts

Parenchymal patterns characteristic of dense breasts are known to degrade the mammographic detection of small breast cancers and microcalcifications. This arises from large variations in exposure of the film, resulting in reduced image contrast over areas of suboptimal exposure. Based on sensitometric measurements of mammograms from a typical patient population, it is shown that over 60% of a typical mammogram in Wolfe's DY classification was found to be exposed suboptimally, suggesting a significant margin for improving mammography for these patients. In order to address this problem, a prototype mammographic version of scanning equalisation radiography (MSER) has been developed, which delivers a patient-specific spatially non-uniform distribution of breast exposure, adjusted to maintain optimal film exposure and contrast over the entire mammogram. Anthropomorphic phantom MSER images show a marked improvement in subjective image quality relative to conventional mammograms, while exhibiting a similar radiation risk. The detection of small microcalcifications and fibrils over clinically significant breast densities is found to be improved by factors eight and four, respectively. Such a system may be clinically practical through the use of multiple-beam equalisation methods with available X-ray tube technology.