Screening Algorithms in Dense Breasts: AJR Expert Panel Narrative Review.

Screening mammography reduces breast cancer mortality; however, when used to examine women with dense breasts, its performance and resulting benefits are reduced. Increased breast density is an independent risk factor for breast cancer. Digital breast tomosynthesis (DBT), ultrasound (US), molecular breast imaging (MBI), MRI, and contrast-enhanced mammography (CEM) each have shown improved cancer detection in dense breasts when compared with 2D digital mammography (DM). DBT is the preferred mammographic technique for producing a simultaneous reduction in recalls (i.e., additional imaging). US further increases cancer detection after DM or DBT and reduces interval cancers (cancers detected in the interval between recommended screening examinations), but it also produces substantial additional false-positive findings. MBI improves cancer detection with an effective radiation dose that is approximately fourfold that of DM or DBT but is still within accepted limits. MRI provides the greatest increase in cancer detection and reduces interval cancers and late-stage disease; abbreviated techniques will reduce cost and improve availability. CEM appears to offer performance similar to that of MRI, but further validation is needed. Dense breast notification will soon be a national standard; therefore, understanding the performance of mammography and supplemental modalities is necessary to optimize screening for women with dense breasts.

Effect of age on breast cancer screening using tomosynthesis in combination with digital mammography.

PURPOSE: To determine the effect of tomosynthesis imaging as a function of age for breast cancer screening. METHODS: Screening performance metrics from 13 institutions were examined for 12 months prior to introduction of tomosynthesis (period 1) and compared to those after introduction of tomosynthesis (period 2, range 3-22 months). Screening metrics for women ages 40-49, 50-59, 60-69, and 70+ , included rates per 1000 screens for recalls, biopsies, cancers, and invasive cancers detected. RESULTS: Performance parameters were compared for women screened with digital mammography alone (n = 278,908) and digital mammography + tomosynthesis (n = 173,414). Addition of tomosynthesis to digital mammography produced significant reductions in recall rates for all age groups and significant increases in cancer detection rates for women 40-69. Largest recall rate reduction with tomosynthesis was for women 40-49, decreasing from 137 (95% CI 117-156) to 115 (95% CI 95-135); difference, -22 (95% CI -26 to -18; P < .001). Simultaneous increase in invasive cancer detection rate for women 40-49 from 1.6 (95% CI 1.2-1.9) to 2.7 (95% CI 2.2-3.1) with tomosynthesis (difference, 1.1; 95% CI 0.6-1.6; P < .001) was observed. CONCLUSIONS: Addition of tomosynthesis to digital mammography increased invasive cancer detection rates for women 40-69 and decreased recall rates for all age groups with largest performance gains seen in women 40-49. The similar performance seen with tomosynthesis screening for women in their 40s compared to digital mammography for women in their 50s argues strongly for commencement of mammography screening at age 40 using tomosynthesis.

Preoperative Tomosynthesis-guided Needle Localization of Mammographically and Sonographically Occult Breast Lesions.

PURPOSE: To assess the feasibility and accuracy of digital breast tomosynthesis (DBT)-guided needle localization for DBT-detected suspicious abnormalities not visualized with other modalities and to analyze the imaging and pathologic characteristics of abnormalities detected only with DBT to determine the positive predictive value for malignancy. MATERIALS AND METHODS: This HIPAA-compliant study was approved by the institutional review board, and the requirement to obtain informed consent was waived. A retrospective query of the imaging database identified 34 consecutive women (average age, 55 years; age range, 28-84 years) with 36 lesions who underwent DBT-guided needle localization between April 2011 and January 2013 with use of commercially available equipment. Imaging findings and medical records were reviewed. Findings that were attributable to previous surgical changes were classified as benign or probably benign and excluded from analysis because the lesions did not proceed to localization. RESULTS: Architectural distortion was the imaging finding identified in all 36 abnormalities (100%). Findings from pathologic examination after the first attempt at localization were concordant with those from imaging in 35 of the 36 lesions (97%), which is suggestive of appropriate sampling. Histologic findings were malignant in 17 of the 36 lesions (47%; 95% confidence interval: 30.4%, 64.5%). Thirteen of the 17 lesions (76%; 95% confidence interval: 50.1%, 93.1%) were invasive malignancies. Twenty-two of the 36 abnormalities (61%) were either malignant or high-risk lesions (atypical ductal hyperplasia, lobular carcinoma in situ, atypical lobular hyperplasia). CONCLUSION: DBT-guided needle localization is an accurate and feasible method with which to biopsy DBT-detected suspicious architectural distortions not visualized at mammography or sonography. The high risk of malignancy in abnormalities detected only with DBT (47%) confirms that routine biopsy is required for histologic analysis.

Addition of tomosynthesis to conventional digital mammography: effect on image interpretation time of screening examinations.

PURPOSE: To determine the effect of implementing a screening tomosynthesis program on real-world clinical performance by quantifying differences between interpretation times for conventional screening mammography and combined tomosynthesis and mammography for multiple participating radiologists with a wide range of experience in a large academic center. MATERIALS AND METHODS: In this HIPAA-compliant, institutional review board-approved study, 10 radiologists prospectively read images from screening digital mammography or screening combined tomosynthesis and mammography examinations for 1-hour-long uninterrupted sessions. Images from 3665 examinations (1502 combined and 2163 digital mammography) from July 2012 to January 2013 were interpreted in at least five sessions per radiologist per modality. The number of cases reported during each session was recorded for each reader. The experience level for each radiologist was also correlated to the average number of cases reported per hour. Analysis of variance was used to assess the number of studies interpreted per hour. A linear regression model was used to evaluate correlation between breast imaging experience and time taken to interpret images from both modalities. RESULTS: The mean number of studies interpreted in hour was 23.8 ± 0.55 (standard deviation) (range, 14.4-40.4) for combined tomosynthesis and mammography and 34.0 ± 0.55 (range, 20.4-54.3) for digital mammography alone. A mean of 10.2 fewer studies were interpreted per hour during combined tomosynthesis and mammography compared with digital mammography sessions (P < .0001). The mean interpretation time was 2.8 minutes ± 0.9 (range, 1.5-4.2 minutes) for combined tomosynthesis and mammography and 1.9 minutes ± 0.6 (range, 1.1-3.0) for digital mammography; interpretation time with combined tomosynthesis and mammography was 0.9 minute longer (47% longer) compared with digital mammography alone (P < .0001). With the increase in years of breast imaging experience, the overall additional time required to read images from combined tomosynthesis and mammography examinations decreased (R(2) = 0.52, P = .03). CONCLUSION: Addition of tomosynthesis to mammography results in increased time to interpret images from screening examinations compared with time to interpret images from conventional digital mammography alone.

Percutaneous breast biopsy: effect on short-term quality of life.

PURPOSE: To examine the effects of percutaneous breast biopsy on short-term quality of life. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant prospective study. From December 1, 2007, through February 28, 2010, women undergoing percutaneous breast biopsy in an academic medical center were recruited to participate in a mixed-mode survey 2-4 days after biopsy. Patients described their biopsy experience by using the Testing Morbidities Index (TMI), a validated instrument for assessing short-term quality of life related to diagnostic testing. The scale ranged from 0 (worst possible experience) to 100 (no adverse effects). Seven attributes were assessed: pain or discomfort before and during testing, fear or anxiety before and during testing, embarrassment during testing, and physical and mental function after testing. Demographic and clinical information were also collected. Univariate and multivariate linear regression analyses were performed to identify significant predictors of TMI score. RESULTS: In 188 women (mean age, 51.4 years; range, 22-80 years), the mean TMI score (±standard deviation) was 82 ± 12. Univariate analysis revealed age and race as significant predictors of the TMI score (P < .05). In the multivariate model, only patient age remained a significant independent predictor (P = .001). TMI scores decreased by approximately three points for every decade decrease in patient age, which suggests that younger women were more adversely affected by the biopsy experience. CONCLUSION: Younger patient age is a significant predictor of decreased short-term quality of life related to percutaneous breast biopsy procedures. Tailored prebiopsy counseling may better prepare women for percutaneous biopsy procedures and improve their experience.

Patient outcomes in canceled MRI-guided breast biopsies.

OBJECTIVE: The reported frequency of aborted MRI-guided breast biopsies ranges from 8% to 17%, usually secondary to nonvisualization at attempted biopsy. Our study examines the frequency of MRI-guided breast biopsies aborted because of lesion nonvisualization and the subsequent risk of malignancy. MATERIALS AND METHODS: We identified 350 patients and 445 lesions scheduled for MRI-guided biopsy between January 1, 2007, and December 31, 2009. Medical records and imaging studies were reviewed to ascertain patient demographics, lesion and imaging characteristics, and subsequent pathology results. Chi-square statistics were calculated for patient level analyses. RESULTS: MRI-guided biopsies were aborted in 13% (56/445) of lesions and 15% (53/350; 95% CI, 11.6-19.3%) of patients because of nonvisualization of the biopsy target at the time of attempted biopsy. Of these 53 patients, 50 patients had follow-up data available. Malignancy was subsequently diagnosed in five of those 50 patients (10%; 95% CI, 3.3-21.8%), three with invasive ductal carcinomas and two with ductal carcinoma in situ. The mean time to malignant diagnosis from the date of aborted biopsy was 2.6 months (range, 1.1-6.9 months). CONCLUSION: Informed consent for MRI-guided breast biopsies should include discussion of biopsy cancellation because of nonvisualization of the target lesion. The low yet significant risk of malignancy in patients subsequent to an aborted MRI-guided breast biopsy warrants short-term follow-up MRI after a canceled biopsy.

Diagnostic accuracy and recall rates for digital mammography and digital mammography combined with one-view and two-view tomosynthesis: results of an enriched reader study.

OBJECTIVE: The purpose of this study was to compare two methods of combining tomosynthesis with digital mammography by assessing diagnostic accuracy and recall rates for digital mammography alone and digital mammography combined with one-view tomosynthesis and two-view tomosynthesis. SUBJECTS AND METHODS: Three hundred ten cases including biopsy-proven malignancies (51), biopsy-proven benign findings (47), recalled screening cases (138), and negative screening cases (74) were reviewed by 15 radiologists sequentially using digital mammography, adding one-view tomosynthesis, and then two-view tomosynthesis. Cases were assessed for recall and assigned a BI-RADS score and probability of malignancy for each imaging method. Diagnostic accuracy was assessed using receiver operating characteristic (ROC) analysis. Screening recall rates were compared using pooled logistical regression analysis. A p value of < 0.0167 was considered significant. RESULTS: The area under the ROC curve (AUC) for digital mammography (DM), DM plus one-view tomosynthesis, and DM plus two-view tomosynthesis was 0.828, 0.864, and 0.895, respectively. Both one-view and two-view tomosynthesis plus DM were significantly better than DM alone (Δ AUCs 0.036 [p = 0.009] and 0.068 [p < 0.001]). Average noncancer recall rates for digital mammography, DM plus one-view tomosynthesis, and DM plus two-view tomosynthesis were 44.2%, 27.2%, and 24.0%, respectively. Combined with DM, one-view and two-view tomosynthesis both showed significantly lower noncancer recall rates than digital mammography alone (p < 0.001). Digital mammography with two-view tomosynthesis showed a significantly lower recall rate than digital mammography with one-view tomosynthesis (p < 0.001). Diagnostic accuracy for dense (Δ AUC, 0.091%; p < 0.001) and nondense (Δ AUC, 0.035%; p = 0.001) breasts improved with DM plus two-view tomosynthesis compared with digital mammography alone. Compared with digital mammography, diagnostic sensitivity for invasive cancers increased with the addition of both one-view (Δ12.0%, p < 0.001) and two-view (Δ21.7%, p < 0.001) tomosynthesis. CONCLUSION: The addition of one-view tomosynthesis to conventional digital mammography improved diagnostic accuracy and reduced the recall rate; however, the addition of two-view tomosynthesis provided twice the performance gain in diagnostic accuracy while further reducing the recall rate.

Digital breast tomosynthesis in the analysis of fat-containing lesions.

Digital breast tomosynthesis (DBT) is rapidly emerging as an important clinical tool for both screening and diagnosis. DBT improves upon mammography by depicting breast tissue on a dynamic sequence of cross-sectional images reconstructed in planes corresponding to their mammographic planes of acquisition. DBT results in markedly reduced summation of overlapping tissue and depicts the margins of masses in far greater detail than mammography. Fat is commonly recognized in both benign and malignant breast masses at DBT, even when no fat is appreciated at mammography. In cases of encapsulated fat-containing masses, the increased detail at DBT often allows the radiologist to definitively classify a mass as benign (eg, lipoma, hamartoma, galactocele, lipid cyst) when mammographic findings alone are equivocal, thereby avoiding unnecessary biopsy or workup. However, when learning to read DBT images, many radiologists misinterpret this rule, mistaking the presence of any fat within a mass for an indication of benignity or an artifact and falsely concluding that an otherwise suspicious mass is not worrisome. If fat seen in breast masses at DBT is not appropriately analyzed, malignant breast masses may be incorrectly classified as probably or even definitely benign. With use of radiologic-pathologic correlation, the authors illustrate cases in which the presence of fat can help correctly classify a mass as benign, and pitfalls in which the presence or absence of fat within a mass is irrelevant and should not influence analysis.

To do or not to do: axillary nodal evaluation after ACOSOG Z0011 Trial.

Methods of axillary evaluation in invasive breast cancer continue to evolve. The recent American College of Surgeons Oncology Group Z0011 Trial is a prospective, randomized, multicenter trial that compared the survival and locoregional recurrence rates after complete axillary lymph node dissection (ALND) versus sentinel node biopsy (SNB) alone in women with a positive sentinel node in an effort to avoid the complications associated with ALND. As the results of this trial are implemented clinically, affecting surgical management of axillary metastatic disease, radiologists may need to redefine their role in the preoperative assessment of the axilla. Before the Z0011 trial, breast imagers worked to identify axillary metastases preoperatively, allowing appropriate patients to proceed directly to ALND and avoiding the need for SNB. However, the Z0011 trial concluded that ALND may not be necessary in women with metastatic axillary disease who meet the trial criteria. In the Z0011 trial, after 6 years of median follow-up there was no difference in either locoregional recurrence or survival among the women who underwent SNB alone compared with those who underwent ALND, suggesting that ALND is unnecessary in a subset of women with a positive node at SNB. These results raise questions about how aggressively radiologists should pursue percutaneous sampling of axillary nodes, as some practitioners conclude that, in an otherwise eligible woman, positive results from imaging-guided percutaneous biopsy preclude a Z0011 trial-directed pathway. Debate about the best way to implement the results of the Z0011 trial into daily clinical practice exists. It is important for breast imagers to work closely with breast surgeons to provide the most appropriate treatment course for each patient.

Breast cancer screening using tomosynthesis in combination with digital mammography.

IMPORTANCE: Mammography plays a key role in early breast cancer detection. Single-institution studies have shown that adding tomosynthesis to mammography increases cancer detection and reduces false-positive results. OBJECTIVE: To determine if mammography combined with tomosynthesis is associated with better performance of breast screening programs in the United States. DESIGN, SETTING, AND PARTICIPANTS: Retrospective analysis of screening performance metrics from 13 academic and nonacademic breast centers using mixed models adjusting for site as a random effect. EXPOSURES: Period 1: digital mammography screening examinations 1 year before tomosynthesis implementation (start dates ranged from March 2010 to October 2011 through the date of tomosynthesis implementation); period 2: digital mammography plus tomosynthesis examinations from initiation of tomosynthesis screening (March 2011 to October 2012) through December 31, 2012. MAIN OUTCOMES AND MEASURES: Recall rate for additional imaging, cancer detection rate, and positive predictive values for recall and for biopsy. RESULTS: A total of 454,850 examinations (n=281,187 digital mammography; n=173,663 digital mammography + tomosynthesis) were evaluated. With digital mammography, 29,726 patients were recalled and 5056 biopsies resulted in cancer diagnosis in 1207 patients (n=815 invasive; n=392 in situ). With digital mammography + tomosynthesis, 15,541 patients were recalled and 3285 biopsies resulted in cancer diagnosis in 950 patients (n=707 invasive; n=243 in situ). Model-adjusted rates per 1000 screens were as follows: for recall rate, 107 (95% CI, 89-124) with digital mammography vs 91 (95% CI, 73-108) with digital mammography + tomosynthesis; difference, -16 (95% CI, -18 to -14; P < .001); for biopsies, 18.1 (95% CI, 15.4-20.8) with digital mammography vs 19.3 (95% CI, 16.6-22.1) with digital mammography + tomosynthesis; difference, 1.3 (95% CI, 0.4-2.1; P = .004); for cancer detection, 4.2 (95% CI, 3.8-4.7) with digital mammography vs 5.4 (95% CI, 4.9-6.0) with digital mammography + tomosynthesis; difference, 1.2 (95% CI, 0.8-1.6; P < .001); and for invasive cancer detection, 2.9 (95% CI, 2.5-3.2) with digital mammography vs 4.1 (95% CI, 3.7-4.5) with digital mammography + tomosynthesis; difference, 1.2 (95% CI, 0.8-1.6; P < .001). The in situ cancer detection rate was 1.4 (95% CI, 1.2-1.6) per 1000 screens with both methods. Adding tomosynthesis was associated with an increase in the positive predictive value for recall from 4.3% to 6.4% (difference, 2.1%; 95% CI, 1.7%-2.5%; P < .001) and for biopsy from 24.2% to 29.2% (difference, 5.0%; 95% CI, 3.0%-7.0%; P < .001). CONCLUSIONS AND RELEVANCE: Addition of tomosynthesis to digital mammography was associated with a decrease in recall rate and an increase in cancer detection rate. Further studies are needed to assess the relationship to clinical outcomes.

Assessing radiologist performance using combined digital mammography and breast tomosynthesis compared with digital mammography alone: results of a multicenter, multireader trial.

PURPOSE: To compare radiologists' diagnostic accuracy and recall rates for breast tomosynthesis combined with digital mammography versus digital mammography alone. MATERIALS AND METHODS: Institutional review board approval was obtained at each accruing institution. Participating women gave written informed consent. Mediolateral oblique and craniocaudal digital mammographic and tomosynthesis images of both breasts were obtained from 1192 subjects. Two enriched reader studies were performed to compare digital mammography with tomosynthesis against digital mammography alone. Study 1 comprised 312 cases (48 cancer cases) with images read by 12 radiologists; study 2, 312 cases (51 cancer cases) with 15 radiologists. Study 1 readers recorded only that an abnormality requiring recall was present; study 2 readers had additional training and recorded both lesion type and location. Diagnostic accuracy was compared with receiver operating characteristic analysis. Recall rates of noncancer cases, sensitivity, specificity, and positive and negative predictive values determined by analyzing Breast Imaging Reporting and Data System scores were compared for the two methods. RESULTS: Diagnostic accuracy for combined tomosynthesis and digital mammography was superior to that of digital mammography alone. Average difference in area under the curve in study 1 was 7.2% (95% confidence interval [CI]: 3.7%, 10.8%; P < .001) and in study 2 was 6.8% (95% CI: 4.1%, 9.5%; P < .001). All 27 radiologists increased diagnostic accuracy with addition of tomosynthesis. Recall rates for noncancer cases for all readers significantly decreased with addition of tomosynthesis (range, 6%-67%; P < .001 for 25 readers, P < .03 for all readers). Increased sensitivity was largest for invasive cancers: 15% and 22% in studies 1 and 2 versus 3% for in situ cancers in both studies. CONCLUSION: Addition of tomosynthesis to digital mammography offers the dual benefit of significantly increased diagnostic accuracy and significantly reduced recall rates for noncancer cases. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120674/-/DC1.

Lesions of the skin and superficial tissue at breast MR imaging.

Although numerous studies have outlined the benefits of contrast material-enhanced magnetic resonance (MR) imaging for the detection of breast parenchymal findings, the assessment of lesions of the skin and superficial tissue at breast MR imaging has largely been overlooked. Such lesions, both benign and malignant, are commonly encountered at breast MR imaging, and their detection and diagnosis are often imperative. These lesions include superficial, locally extensive, inflammatory, and recurrent breast cancers; iatrogenic changes; sebaceous cysts; and less prevalent diseases such as granulomatous mastitis and angiosarcomas, among others. As MR imaging continues to be used with increasing frequency in both the screening and diagnostic settings, these lesions will be encountered more often; consequently, a better understanding of which lesions may be ignored and which require further evaluation will become increasingly important. Frequently, MR imaging alone may not clearly indicate the cause of lesions of the breast skin and superficial tissue. However, radiologists should thoroughly assess such lesions, taking into consideration the spectrum of possible causes. Mammography, ultrasonography, consultation with clinicians or dermatologists regarding physical examination findings, and, when necessary, correlation with pathologic findings in biopsy specimens may be used in conjunction with MR imaging to establish both the importance of these lesions and their definitive diagnoses.

Detecting nonpalpable recurrent breast cancer: the role of routine mammographic screening of transverse rectus abdominis myocutaneous flap reconstructions.

PURPOSE: To perform a retrospective cohort study to determine the rates of recall and cancer detection and then to develop a decision analytic model to evaluate the effectiveness of routine screening of transverse rectus abdominis myocutaneous (TRAM) flap reconstructions. MATERIALS AND METHODS: This study was approved by the institutional review board, and the methods comply with HIPAA regulations. A retrospective search of the institutional mammographic results database was done to identify bilateral screening mammographic examinations obtained from January 1, 1999, through July 15, 2005. The search included the term TRAM; the recall and cancer detetion rates were then detected. Subsequently, a decision analytic model was constructed to evaluate a hypothetical cohort of women with TRAM flap reconstructions. RESULTS: Of 554 mammograms (265 TRAM flap reconstructions), 546 (98.6%) had negative results (Breast Imaging Reporting and Data System category 1 or 2). Eight (1.4%) had positive test results (Breast Imaging Reporting and Data System category 0, 3, 4, or 5). All suspicious lesions underwent biopsy and had benign pathologic results. No interval breast cancers were identified. The detection rate for nonpalpable recurrent breast cancer was 0% (exact 95% confidence interval: 0.0%, 1.4%). According to decision analysis, screening would help detect an estimated 12 additional recurrent cancers per 1000 women screened, providing an additional 1.6 days of life expectancy for the screened cohort. Under base-case conditions, screening of TRAM flap reconstructions is less effective than screening asymptomatic women in their 40s. Sensitivity analysis revealed that a benefit equivalent to that of screening asymptomatic women in their 40s was achievable under conditions related to estimates of screening effectiveness and cancer detection rate. CONCLUSION: Routine screening mammography of TRAM flap reconstructions has a very low detection rate for nonpalpable recurrent breast cancer. Decision analysis indicates that screening such women is less effective than screening asymptomatic women in their 40s for primary breast cancer.

Analysis of the mammographic and sonographic features of pseudoangiomatous stromal hyperplasia.

OBJECTIVE: The purpose of this study was to describe the imaging findings in 149 patients with pseudoangiomatous stromal hyperplasia (PASH) who had undergone at least 4 years of clinical follow-up for detection of subsequent malignancy. CONCLUSION: PASH is a common entity that presents with benign imaging features without evidence of subsequent malignant potential. At our institution, in the absence of suspicious features a diagnosis of PASH at core biopsy is considered sufficient, and surgical excision has been obviated.

Digital mammography: novel applications.

This article discusses the limitations of current imaging modalities in detecting and characterizing tumors in breast tissue. It then explores some potential advanced applications in digital mammography, such as contrast-enhanced mammography, breast tomosynthesis, and dual modality mammographic fusion, that are being investigated to capitalize on the strengths of the digital platform and to realize fully the potential benefits of enhanced detection anticipated from digital mammography.

Blinded comparison of computer-aided detection with human second reading in screening mammography.

OBJECTIVE: The purpose of this study was to compare a human second reader with computer-aided detection (CAD) for the reduction of false-negative cases by a primary radiologist. We retrospectively reviewed our clinical practice. MATERIALS AND METHODS: We found that 6,381 consecutive screening mammograms were interpreted by a primary reader. This radiologist then reinterpreted the studies using CAD ("CAD reader"). A second human reader who was blinded to the CAD results but knowledgeable of the primary reader's findings reviewed the studies, looking for abnormalities not seen by the first reader. RESULTS: Two cancers were called back by the second human reader that were not called back by the CAD reader; however, the CAD system had marked the findings, but they were dismissed by the primary reader. Because of the small numbers, the difference between the CAD and second human reader was not statistically significant. The CAD and human second readers increased the recall rates 6.4% and 7.2% (p = 0.70), respectively, and the biopsy rates 10% and 14.7%. The positive predictive value was 0% (0/3) for the CAD reader and was 40% (2/5) for the human second reader. The relative increases in the cancer detection rate compared with the primary reader's detection rate were 0% for the CAD reader and 15.4% (2/13) for the human second reader (p = 0.50). CONCLUSION: A human second reader or the use of a CAD system can increase the cancer detection rate, but we found no statistical difference between the two because of the small sample size. A possible benefit from a human second reader is that CAD systems can only point to possible abnormalities, whereas a human must determine the significance of the finding. Having two humans review a study may increase detection rates due to interpreter--hence, perceptual--variability and not just increased detection.