A recent American study reported in the British Medical Journal concluded that mammography is not particularly useful in that it does not appear to save lives. We agree but suggest that that the study does go far enough and that the study chose a rather harsh measure.
No thinking physician would suggest that mammography is foolproof. In fact it is the least dependable commonly used test we have. It causes nearly as much harm as it prevents because of combined error rates approaching on third (false positives and false negatives). However, mammography is improving and so are needle biopsying techniques. If thought of as an indicator rather than showing proof of disease it is useful. But the treating physician must not overly aggressive and should take mammography results for what they are- one piece of information to be used in conjunction with risk assessment and physical exam of the breasts.
Mammography is merely a sophisticated low dose method of soft tissue x-ray exam. Radiographic diagnostics of soft tissue is generally imperfect. X-rays pick up differences in density and in soft tissue differences are often very subtle or non-existent between tumor and normal tissue.
The standard of care for women with breast lumps is nearly written in stone. There must be some form of disposition of the mass. It must be needled or removed. If ultrasound suggests a cyst, needling is the safest approach but watchful waiting is acceptable. If not cystic it may be needle biopsied but a better course is excision biopsy. Unfortunately many women end up getting needless breast biopsies but currently we can't avoid doing so. If a woman has a palpable mass, mammography is of little assistance is the disposition of that mass but is useful in determining if there are other suspicious areas of either breast. Remember that breast cancer can be multi-focal or even bilateral.
The standard of care for women with suspicious mammography findings alone is not so clear. Interpretation is often a problem, even as techniques improve. Biopsy of mammogram lesions is no small task either. Needle biopsies may miss the tumor. The surgeon asked to do an excisional biopsy must take enough tissue to be well around the lesion. Thus removal of what is often a benign lesion, or even a non-existent one, is destructive. Many suspicious mammogram lesions turn out to be benign. Yet findings of a suspicious lesion on mammography cannot be ignored! Many successful malpractice suits have arisen from such inadvertence.
The authors point out that treatment for breast cancer has improved, primarily with use of chemotherapy and most importantly with use of tamoxifen. This has blurred the statistical usefulness of mammography since women with larger lesions at time of diagnosis now live considerably longer.
We are left to conclude that mammography is a poor test with disappointing accuracy. However, not unlike other areas of soft tissue radiography, techniques can only improve a little. The usual indicators of a suspicious lesion are stippling (small areas of calcium deposits), distortion of anatomy, or sometimes the presence of a non-calcified but identifiable mass. Breast cancers often have nearly identical properties as surrounding tissue and cannot be distinguished at all.
For some women, mammography has undoubtedly been a boon. Those who benefit most are those who are found to have a small but definable lesion, which turns out to be a very early cancer (carcinoma in situ). For these few, lumpectomy is often adequate and they are saved not only the likelihood that their cancer will enlarge and metastasize but the mutilation of a mastectomy. The finding of a larger lesion may be beneficial but the benefits are less easily defined. Such discoveries have to be weighed against the cost and the disfigurement resulting from false positives.
The American Cancer Society has promoted mammography and it has become a massive economic boondoggle. Instead of focusing on women with increased risk, their guidelines promote unnecessary exams on those with less risk. Some of the problems that we see are:
1. Inadequate physical exams done in conjunction with mammography, especially when women go to a so-called "breast center" where exams are often carried out by non-physicians.
2. Lack of quality controls as to method or those who are qualified to read the exams.
3. Failure of adequate reporting of suspicious lesions. Is a written report of a truly suspicious lesion enough? Obviously not!
4. Failure of gynecologists and family practitioners to refer women with suspicious lesions on mammography (or dominant masses on physical exam) to surgeons. General surgeons remain the only specialists qualified to deal with breast disease.
Our conclusion-this study adds nothing. Mammography is imperfect but it is the best we have. Defining more accurately who can benefit might be useful. Timing exams based on risk might help. Many women probably get no benefit out of yearly mammography, and though radiation exposure is not nearly as great as it once was, it is not something to ignore.
British Medical Journal, 2002, feb2;324(7332):255
