|
Page: Results
Main article
| Home > Preventive Medicine > Results |
Often women are quite distressed to be called back for a diagnostic mammogram. Most of these recalls will be false positive results. It helps to know these approximate statistics: of every 1,000 U.S. women who are screened, about 7% (70) will be called back for a diagnostic session (although some studies estimate the number closer to 10%-15%). About 10 of these will be referred for a biopsy; the remaining 60 are found to be of benign cause. Of the 10 referred for biopsy, about 3.5 will have a cancer and 6.5 will not. Of the 3.5 who do have cancer, about 2 have a low stage cancer that will be essentially cured after treatment. Mammogram results are often expressed in terms of the BI-RADS Assessment Category, often called a "BI-RADS score." The categories range from 0 (Incomplete) to 6 (Known biopsy – proven malignancy). In the UK mammograms are scored on a scale from 1-5 (1 = normal, 2 = benign, 3 = indeterminate, 4 = suspicious of malignancy, 5 = malignant).
The rates of abnormal and false-positive mammogram results are far lower in countries other than the U.S. that have adopted different quality standards. For example, in Holland, only about 1% of mammograms yield abnormal result. As a result, false-positives are much less common. Despite the higher rates of false-positives in the U.S., women are about as likely to die from breast cancer in the U.S. as in Holland and elsewhere in Europe.
While mammography is the only breast cancer screening method that has been shown to save lives, it is not perfect. Estimates of the numbers of cancers missed by mammography are usually around 10%-20%. This means that of the 350 per 100,000 women who have breast cancer, about 35-70 will not be seen by mammography. Reasons for not seeing the cancer include observer error, but more frequently it is due to the fact that the cancer is hidden by other dense tissue in the breast and even after retrospective review of the mammogram, cannot be seen. Furthermore, one form of breast cancer, lobular cancer, has a growth pattern that produces shadows on the mammogram which are indistinguishable from normal breast tissue.
Computer-assisted analysis is being tested to decrease the number of cases of cancer that are missed in mammograms. In one test, a computer identified 71% of the cases of cancer that had been missed by physicians. However, the computer also flagged twice as many non-cancerous masses than the physicians did. In a second study of a larger set of mammograms, a computer recommended six biopsies that physicians did not. All six turned out to be cancers that would have been missed. (Destounis, et al., 2004)
While data are accumulating suggesting that CAD can find a few additional cancers, this should be put in perspective. The additional find rate was 20%, thus in a group of 1,000 women who will have about 4 cancers, CAD may help find an additional 0.8. The types of additional cancers that may be found are likely to be early and small. As of 2006, there have been no data to show that finding these additional cancers will have any effect on survival rate. Some feel that these cancers are likely to be found at the next screening, still at a curable stage, and therefore it remains to be proven whether CAD will be eventually found to have any effect on patient outcome.
|
Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
|