Tumor location and detectability in mammographic screening

The adequacy of a film mammogram that does not visualize the retromammary space or ribs has concerned radiologists. The 79 prevalent cancers detected in the 10,000 self-referred woman at the University of Michigan Breast Cancer Detection Demonstration Project were analyzed for number of films required to detect the cancer, relationship of the cancer to the posterior edge of the film, number of occult lesions, tumor size, histologic type, sensitivity of detection method, and number of interval carcinomas. The mammograms were obtained using a dedicated mammographic machine and the upright position, with visualization of the anterior axillary fold on the mediolateral view. The ribs were not imaged. Of the 79 cancers, 76 were detectable on the mammogram. All were visualized on the mediolateral view, while three were not imaged on the craniocaudal view. Twelve percent of the cancers were within 1 cm of the posterior edge of the film. Only six "interval" carcinomas were found in the 10,000 patients within the year of the initial examinations; these women had dense P2 or DY mammographic parenchymal patterns. The detected cancers were smaller and had a significantly higher percentage of noninvasive cancers than in a symptomatic clinical population. Thus, properly exposed film mammograms using vigorous breast compression examine the breast adequately without visualizing the ribs.     

Hormone replacement therapy and mammographic screening

The benefits of hormone replacement therapy (HRT) with oestrogen are well known and have led to widespread usage of HRT in post-menopausal women. There is an increased relative risk of breast cancer with prolonged HRT use of 1.7 at worst and this does not warrant more frequent screening. HRT itself makes mammographic screening less effective by adversely affecting both the sensitivity and specificity of screening mammography.A number of large studies have shown a reduction in the sensitivity of screening mammography of between 7% and 21% in current HRT users. This reduction in sensitivity is seen only in women over the age of 50 and is more marked when using single view mammography. The reduction in sensitivity is largely confined to those women who have a dense mammographic background pattern while on HRT. HRT use is also associated with a reduction in specificity of between 12% and almost 50%. This reduction in specificity is mainly found at incident screens. What can be done to minimize the adverse effects of HRT on mammographic screening? The imminent introduction of two views at all screens within the National Health Breast Screening Programme will be helpful. Short-term cessation of HRT use may deter attendance for screening by HRT users and is unproven. Combined oestrogen and progesterone preparations taken continuously appear to be particularly associated with adverse breast screening performance, while tibolone may have little effect on mammographic density. Manipulation of the type of HRT preparations used may allow the adverse effects of HRT on breast screening to be reduced.     

Denoising and enhancing digital mammographic images for visual screening.

Dense regions in digital mammographic images are usually noisy and have low contrast, and their visual screening is difficult. This paper describes a new method for mammographic image noise suppression and enhancement, which can be effective particularly for screening image dense regions. Initially, the image is preprocessed to improve its local contrast and the discrimination of subtle details. Next, image noise suppression and edge enhancement are performed based on the wavelet transform. At each resolution, coefficients associated with noise are modelled by Gaussian random variables; coefficients associated with edges are modelled by Generalized Laplacian random variables, and a shrinkage function is assembled based on posterior probabilities. The shrinkage functions at consecutive scales are combined, and then applied to the wavelets coefficients. Given a resolution of analysis, the image denoising process is adaptive (i.e. does not require further parameter adjustments), and the selection of a gain factor provides the desired detail enhancement. The enhancement function was designed to avoid introducing artifacts in the enhancement process, which is essential in mammographic image analysis. Our preliminary results indicate that our method allows to enhance local contrast, and detect microcalcifications and other suspicious structures in situations where their detection would be difficult otherwise. Compared to other approaches, our method requires less parameter adjustments by the user.     

Breast cancer risk prediction model: a nomogram based on common mammographic screening findings

Objectives

To develop a prediction model for breast cancer based on common mammographic findings on screening mammograms aiming to reduce reader variability in assigning BI-RADS.

Methods

We retrospectively reviewed 352 positive screening mammograms of women participating in the Dutch screening programme (Nijmegen region, 2006–2008). The following mammographic findings were assessed by consensus reading of three expert radiologists: masses and mass density, calcifications, architectural distortion, focal asymmetry and mammographic density, and BI-RADS. Data on age, diagnostic workup and final diagnosis were collected from patient records. Multivariate logistic regression analyses were used to build a breast cancer prediction model, presented as a nomogram.

Results

Breast cancer was diagnosed in 108 cases (31 %). The highest positive predictive value (PPV) was found for spiculated masses (96 %) and the lowest for well-defined masses (10 %). Characteristics included in the nomogram are age, mass, calcifications, architectural distortion and focal asymmetry.

Conclusion

With our nomogram we developed a tool assisting screening radiologists in determining the chance of malignancy based on mammographic findings. We propose cutoff values for assigning BI-RADS in the Dutch programme based on our nomogram, which will need to be validated in future research. These values can easily be adapted for use in other screening programmes.

Key points

? There is substantial reader variability in assigning BI-RADS in mammographic screening. ? There are no strict guidelines linking mammographic findings to BI-RADS categories. ? We developed a model (nomogram) predicting the presence of breast cancer. ? Our nomogram is based on common findings on positive screening mammograms. ? The nomogram aims to assist screening radiologists in assigning BI-RADS categories.     

Breast compression and reported pain during mammographic screening

IntroductionWe aimed to investigate the association between breast compression and experienced pain during mammographic screening.MethodsUsing a questionnaire, we collected information on pain experienced during mammography from 1155 women screened in Akershus, February–March 2018, as a part of BreastScreen Norway. The questionnaire provided information on pain using a numeric rating scale (NRS, 0–10) and related factors. Data on compression force (Newton, N), pressure (kilopascal, kPa) and breast characteristics were extracted from the DICOM-header and a breast density software. Log-binomial regression was used to determine the relative risk (RR) of severe versus mild/moderate experienced pain associated with compression parameters, adjusting for breast characteristics and related factors.ResultsMean score of experienced pain was 2.2, whereas 6% of the women reported severe pain (≥7) during the examination. High body mass index (BMI) (≥27.3 kg/m²) was associated with a higher RR of pain scores ≥7 (RR 1.86, 95%CI 1.02–3.36) compared to medium BMI (23.7–27.2 kg/m²). Low compression pressure (4.0–10.2 kPa) was associated with a higher RR of severe pain (RR 2.93, 95%CI 1.39–6.20), compared with medium compression pressure (10.3–13.5 kPa) after adjusting for contact area, age, compressed breast thickness, volumetric breast density and BMI. The risk of severe versus mild/moderate pain (≥7 versus <7) decreased by 2% with increasing compression force (RR 0.98, 95%CI 0.97–1.00).ConclusionWomen reported low levels of pain during mammography. Further knowledge about factors affecting experienced pain is needed to personalize the examination to the individual woman.Implications for practicePain in shoulder(s) and/or neck prior to screening should be considered by the radiographers in a practical screening setting. A compression force of 100–140 N and pressure of 10.3–13.5 kPa are acceptable with respect to reported pain during mammography.     

Assessment of mammographic film processor performance in a hospital and mobile screening unit.

In contrast to the majority of mammographic breast screening programmes, film processing at this centre occurs on site in both hospital and mobile trailer units. Initial (1989) quality control (QC) sensitometric tests revealed a large variation in film processor performance in the mobile unit. The clinical significance of these variations was assessed and acceptance limits for processor performance determined. Abnormal mammograms were used as reference material and copied using high definition 35 mm film over a range of exposure settings. The copies were than matched with QC film density variation from the mobile unit. All films were subsequently ranked for spatial and contrast resolution. Optimal values for processing time of 2 min (equivalent to film transit time 3 min and developer time 46 s) and temperature of 36 degrees C were obtained. The widespread anomaly of reporting film transit time as processing time is highlighted. Use of mammogram copies as a means of measuring the influence of film processor variation is advocated. Careful monitoring of the mobile unit film processor performance has produced stable quality comparable with the hospital based unit. The advantages of on site film processing are outlined. The addition of a sensitometric step wedge to all mammography film stock as a means of assessing image quality is recommended.     

Trends in time to completion of mammographic screening and follow-up services

OBJECTIVE: The popular press has raised questions about mammographic capacity in the United States, but mammographic utilization data have not been used to inform these concerns. We used data for the period 1995-2002 from the New Mexico Mammography Project to assess trends in time to completion of mammographic screening and follow-up services. CONCLUSION: The median time to return mammographic screening changed little over time, but trends in the time required to complete recommended follow-up services varied by type of service and urban or rural residence. Further monitoring of time required to complete screening and follow-up services in other regions can inform debates on mammographic capacity.     

Beyond standard mammographic screening: mammography at age extremes, ultrasound, and MR imaging

This article describes the principles and performance of screening mammography and discusses indications for screening before the age of 40 years and after the age of 69 years. Specific definitions of high risk are provided, and the rationale and performance characteristics to dare of supplemental screening with ultrasound or MR imaging are reviewed.     

Mobile mammographic screening of self-referred women: results of 22,540 screenings.

In this mass screening mammography program, self-referred women are accepted for screening only if part of a sponsoring organization. Screening is performed with mobile equipment, often at the work site. Of the first 22,540 screenings, 61% (n = 13,784) were of women aged 35-49 years. Eighty-nine percent (n = 20,025) of the screenings were normal. Of 51 women in whom cancer was found, 38 (75%) were recommended for biopsy on the basis of their initial two-view mammogram. The prevalence of breast cancer generally increased with advancing age but was similar between women aged 35-39 years and those aged 40-49 years. Of the 28 women with complete histologic studies, 43% (n = 12) had pure intraductal cancer and another 43% had negative findings at axillary node dissection. Program costs dictated a $65 fee. Within the design of this program it has been possible to screen large numbers of self-referred women and detect early carcinomas. Program design, however, may make screening more expensive than in a fixed screening site accepting only physician-referred women.     

Rates of recall for thorough examination and surgical biopsy following mammographic screening. Experience with the screening program in Florence

The authors evaluate the recall and biopsy rates during three years of mammographic screening. Recalls (373/25970 = 1.4%) were more frequent at the first (2.3%) than at subsequent screening rounds (1.2%) whereas the predictive value for cancer increased at further screening (11.7 vs 21.7%). Recalls are less frequent in older women, particularly at further screening (40-49 vs 50-59 vs 60-70: 1.7 vs 1.1 vs 0.9%) whereas predictive value is higher (14.8 vs 16.5 vs 36.5%). The presence of mammographic abnormalities accounts for the majority of recalls (1.3%) whereas subjective symptoms other than pain are a less frequent cause of recall (0.2%) although as predictive (22.7 vs 20.4%). Calls for biopsy were limited to cases with suspicion for cancer and this allowed a low biopsy rate (75 = 0.3%) and a high predictive value (92%). The observed results have greatly improved with respect to the past years, due to a higher specificity of recall criteria and to the systematic use of all modern tests (high frequency US, fine-needle aspiration cytology, either manual or US-guided or stereotaxic) at the time of diagnostic assessment. All screening programs, particularly the new ones, should monitor recall and biopsy rates and predictive values as they are indicators of efficiency.     

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.In a previous study in which selected early outcome measures of mammographic screening in Vermont, USA, and Norway were compared, higher recall and interval cancer rates were shown for Vermont than for Norway. The rate of screen-detected cancers did not differ [1]. The findings were consistent with other international studies [2-4]. Different radiological reading procedures have been suggested as a possible reason for the findings [1,2,4].Breast cancer screening involves a series of events that begins with the screening examination (bilateral two-view mammography), and may continue with a recall for diagnostic work-up. The diagnostic work-up may lead to a recommendation for a biopsy, which determines whether the suspect lesion is benign or malignant. In both Vermont and Norway, the decision to recall a female patient is based on the assessment of her initial screening mammogram. In the USA, single reading is the usual practice, while in Norway an independent double reading with consensus is performed, in accordance with the European guidelines [5]. In a single reading, a radiologist decides whether the female patient should be recalled for diagnostic work-up, while in an independent double reading with consensus, two radiologists discuss the findings and a consensus is reached as to whether to recall the patient. In both processes, a final assessment is reached after additional breast imaging (including ultrasound) to determine whether to recommend a biopsy.We surmise that the different procedures for initial assessment will affect the sensitivity and specificity of both the initial and the final assessments. However, this can be difficult to ascertain when comparing countries that also have differing screening intervals. To better understand how differences in the interpretation procedures of screening mammography may influence cancer detection, we have taken a detailed look at the sensitivity and specificity of initial and final assessments in our previously studied cohort of female patients aged 50–69 years who underwent screening mammography in Vermont or Norway during 1997–2003. The aim of this study was to determine and compare the sensitivity and specificity of the initial and final assessments of mammographic screening as practised in Vermont and Norway.     

Systematic mammographic screening for breast cancer in asymptomatic women]

It appears that the mortality rate from breast cancer decreases in 50-year-old (and over) women submitted to mammographic screening. Since 1980, the Unit of Cancer Prevention of the UCL is proposing mammographic screening to women with normal clinical examination but belonging to a "high-risk" group. Among the 5651 mammographies which were performed on 2924 women, 24 biopsies have been proposed and 16 cases of cancer have been diagnosed. 5.5% breast cancers have been detected. This result is consistent with the average figures reported in the screening programmes abroad. Questions about the age at which cancer screening should start and about the number of views that should be taken are also discussed.     

Value of mammographic screening: assessment of studies and opinion

The purpose of mammographic screening is to improve patient survival by detecting cancer at an earlier, more curable stage than is possible with physical examination. Three major studies have been used to assess the effect of mass screening on the survival rates and mortality for patients with breast cancer: the Breast Cancer Detection Demonstration Project, the Health Insurance Plan study, and the study conducted by the Swedish National Board of Health and Welfare. The author reviews these studies, describes statistical biases (lead time, length time, patient self-selection, and overdiagnosis) to be considered in study design and analysis, and discusses briefly risks versus benefits of mammography.     

Mean glandular doses for women undergoing mammographic breast screening in Oyo state, Nigeria

In this work, thermoluminescent dosimeters have been used to measure entrance surface doses (ESDs) of patients undergoing mammographic screening at the University College Hospital, Ibadan, Oyo state. The mean glandular doses (MGDs) were also calculated using the measured ESDs. The results showed that the ESDs ranged from 0.26 mGy to 21.26 mGy for the mediolateral oblique (MLO) views and 0.08 mGy to 5.36 mGy for the craniocaudal (CC) views. The calculated MGD ranged from 0.07 mGy to 3.57 mGy for the MLO views and 0.02 mGy to 0.98 mGy for the CC views. The possible reasons for the large variations in the individual ESD values and MGD values for both views are discussed using patients' data, equipment specific data and the technical parameters used for the examinations. Comparison showed that the mean ESD values and MGD values reported in this work are below published values. The mean of the calculated MGD values is also found to be lower than the recommended guidance level of 3.0 mGy when using grid. 92.5% of the patients had MGD values that are less than 2.5 mGy, hence a national reference MGD value of 2.5 mGy is proposed for Nigeria. Implementation of a dose reduction program in mammographic screening is also suggested because of the observed large variations in patients MGD values.