The missed breast cancer: perceptions and realities

Learning from diagnostic errors: a good way to improve education in radiology

PURPOSE

To evaluate the causes and the main categories of diagnostic errors in radiology as a method for improving education in radiology.

MATERIAL AND METHODS

A Medline search was performed using PubMed (National Library of Medicine, Bethesda, MD) for original research publications discussing errors in diagnosis with specific reference to radiology. The search strategy employed different combinations of the following terms: (1) diagnostic radiology, (2) radiological error and (3) medical negligence. This review was limited to human studies and to English-language literature. Two authors reviewed all the titles and subsequently the abstracts of 491 articles that appeared pertinent. Additional articles were identified by reviewing the reference lists of relevant papers. Finally, the full text of 75 selected articles was reviewed.

RESULTS

Several studies show that the etiology of radiological error is multi-factorial. The main category of claims against radiologists includes the misdiagnoses. Radiologic "misses" typically are one of two types: either missed fractures or missed diagnosis of cancer. The most commonly missed fractures include those in the femur, the navicular bone, and the cervical spine. The second type of "miss" is failure to diagnose cancer. Lack of appreciation of lung nodules on chest radiographs and breast lesions on mammograms are the predominant problems.

CONCLUSION

Diagnostic errors should be considered not as signs of failure, but as learning opportunities.

The use of additional imaging increased specificity and decreased sensitivity in screening mammography

BACKGROUND AND OBJECTIVES

To examine the use of additional imaging after standard mammographic screening views to better understand the value of these additional testing in improving accuracy.

MATERIALS AND METHODS

Statewide population data on screening mammography were used to report accuracy measures at screening and after additional imaging tests. Pathology data from biopsies performed within 1 year following the screening mammogram were used to determine cancer outcome (489 in situ and invasive cancers). Pathologic and population characteristics of women receiving different types of imaging were assessed by chi-square or t-tests. Similar tests compared women with the same imaging and differing outcomes.

RESULTS

Of 77,799 women with screening mammograms 9.9% had additional imaging. Additional imaging reduced false positives from 7,765 (100/1,000 mammograms) to 1,112 (14/1,000 mammograms). The majority of false negatives (82%) occurred in women receiving only screening views, and additional imaging increased the number of false negatives from 82 (1/1,000 mammograms) to 115 (1.5/1,000 mammograms).

CONCLUSION

Additional imaging can reduce unnecessary biopsy but at the cost of some additional false negatives. Additional imaging's potential for improving the sensitivity of screening is limited because most missed cancers occur in women who do not have additional imaging.

A preliminary report on the role of spatial frequency analysis in the perception of breast cancers missed at mammography screening

RATIONALE AND OBJECTIVES

Because several factors are involved in cancer detection, a malignant lesion that is visible on a mammogram will not necessarily be reported by the radiologist reading the case. Indeed, a significant fraction of screening-detected cancers are visible in retrospect, and were perceived by the radiologist when the case was read, but were either reported as benign findings or dismissed as variations of normal breast tissue. In this preliminary report the spatial frequency characteristics of clinically missed lesions are investigated by analyzing the mammogram acquired when the lesion was sent for biopsy and the most recent prior mammogram. For control purposes, the contralateral breast is also analyzed, when this breast is lesion free.

MATERIALS AND METHODS

A database of 70 mammogram cases was assembled. Each case contained eight films: craniocaudal (CC) and mediolateral oblique (MLO) of the breast where a biopsy-proven lesion was found, CC and MLO of the contralateral breast, and CC and MLO of both breasts in the most recent prior mammogram. The dictated reports for all of these cases were obtained. Both benign and malignant lesions were used. The films were digitized and an region of interest surrounding each lesion was segmented from the image for processing using wavelet packets to extract spatial frequency information. The corresponding area was also segmented from the prior mammogram and from the contralateral breast, when this breast was lesion-free. Analysis of variance was used to determine if statistically significant differences existed between the derived features of cancer in the current and prior mammograms.

RESULTS

The data suggests that malignant lesions reported in the prior mammogram as being benign differed from correctly reported malignant lesions and from correctly reported benign lesions. They also differed from nonreported malignant lesions. In addition, the spatial frequency representation of cancer significantly differed in the current and prior cases from the representation of normal breast tissue.

CONCLUSION

Spatial frequency analysis may be useful to differentiate malignant lesions that are reported as benign and correctly reported benign lesions.

Invasive Cancers Detected after Breast Cancer Screening Yielded a Negative Result: Relationship of Mammographic Density to Tumor Prognostic Factors

PURPOSE

To evaluate common breast tumor prognostic characteristics, including estrogen receptor (ER) status, grade, size, and method of detection, in relationship to mammographic density.

MATERIALS AND METHODS

The study involved 121 women who had negative results at both screening mammography and breast physical examination within 17 months before a diagnosis of breast cancer. Mammographic density was classified according to Breast Imaging Reporting and Data System patterns 1 through 4 (where 1 indicates a fatty breast and 4 indicates a dense breast). Axillary nodal status and tumor histologic ER status, histologic grade, size, stage, and method of detection (mammography alone, palpation alone, or both palpation and mammography) were analyzed by density category and tested for statistically significant differences across categories by using analysis of variance.

RESULTS

Statistically significant differences (P <.05) by density category were found for the following variables: ER positivity (15 of 15 tumors in category 1 breasts, 32 of 41 tumors in category 2 breasts, 37 of 49 tumors in category 3 breasts, and eight of 16 tumors in category 4 breasts were ER positive), occurrence of grade 1 tumors (eight, 11, 19, and four tumors in category 1, category 2, category 3, and category 4 breasts, respectively, were grade 1), mean tumor size (11.3, 13.0, 14.7, and 19.7 mm for category 1, category 2, category 3, and category 4 breasts, respectively), detection with mammography alone (13, 31, 36, and four tumors in category 1, category 2, category 3, and category 4 breasts, respectively, were detected with mammography alone), and occurrence of stage I tumors (10, 25, 28, and five tumors in category 1, category 2, category 3, and category 4 breasts, respectively, were stage I).

CONCLUSION

In women with negative results at clinical and mammographic screening within 17 months before breast tumor detection, subsequently diagnosed cancers tend to be ER negative, of higher grade, and larger in size in those with dense tissue patterns than in those with fat patterns.

Increase in cancer detection and recall rates with independent double interpretation of screening mammography

OBJECTIVE

This study reports the increase in cancer detection that resulted from independent double interpretation of screening mammography. Although screening mammography is used to detect occult breast cancer, its sensitivity and specificity are limited. Double interpretation of screening mammograms is one proven method used to improve detection, with studies reporting a 5-15% increase in cancer detection.

MATERIALS AND METHODS

Two radiologists independently double-interpreted 25,369 screening mammograms performed from November 1998 to April 2000. The second reviewer could add but could not delete recalls. The subsequent additional diagnostic imaging was performed in the same way whether generated from the first or the second reviewer. The outcome of each case was determined. The cancer detection rate and sensitivity are reported.

RESULTS

Double interpretation of screening mammograms detected 143 breast malignancies. The second reviewer found nine (6.3%) of 143 cancers and all except one were stage 0 or I. The sensitivity increased from 74.4% to 79.4% with double interpretation. The second reviewer contributed 371 of the 3591 total recalls, increasing the absolute rate of recalls by 1.5% (371/25,369) and the relative rate by 11.5% (371/3220). Six hundred seventy-two total biopsies were performed; 38 were generated by the second interpretation.

CONCLUSION

The relative increase in cancer detection as a result of the second reviewer is 6.3%, similar to the 5-15% reported in the literature. All but one of the nine additional cancers detected were in the early stages.

Blinded review of retrospectively visible unreported breast cancers: an eye-position analysis

PURPOSE

To determine whether unreported retrospectively identified cancers on mammograms receive prolonged visual attention and can be reliably detected in a blinded review.

MATERIALS AND METHODS

Four experienced mammographers performed a blinded review of a test set of 20 retrospective cases where the cancer was not detected until the next mammographic evaluation, 10 prospective cases where the cancer was initially detected, and 10 cancer-free cases. Two views were digitized and displayed on a workstation. The experiment consisted of an initial impression, during which eye position was monitored, and a final impression, during which viewers zoomed on regions of interest and localized suspicious lesions. Eye-position data were analyzed to determine whether retrospectively visible cancers attracted attention to the same degree as prospectively visible cancers. The initial impression used 1,000 msec as the eye-fixation dwell criterion for detecting a lesion.

RESULTS

Initially, 70% of retrospective cancers and 50% of prospective cancers did not attract prolonged visual attention. In prospective cases, detailed examination significantly improved the mean receiver operating characteristic area, from.73 to.88 (P <.01), but in retrospective cases, the mean receiver operating characteristic area barely increased, from.60 to.68, due to a high true-positive-to-false-positive ratio.

CONCLUSION

At blinded review, detection of retrospectively visible cancers was significantly inferior to that of prospective cancers. It cannot be assumed that retrospectively identified cancers are intrinsically detectable, because they do not draw prolonged visual attention during visual search for breast cancers.