The Complexities of Diagnosis
The reason why the numbers are not better for mammograms is related to the types of cancers they detect, and the stage at which they are able to detect them. Most of the breast cancers discovered on regular screening mammograms are slow-growing types found at very early stages, and treatment often begins at a time when there is really little danger from the presence of such a tumor. Slowly growing tumors discovered by clinical examinations are generally found later, when they have grown bigger, but they are still found early enough in the vast majority of cases to be treated with a high degree of success. Faster growing cancers, on the other hand, often grow so large so quickly that they can be detected through touch long before they ever have the chance to be found by a screening mammogram, since these tests are given just once a year.
Mammograms do have an unquestioned ability to find small, relatively underdeveloped breast cancer tumors at an earlier stage than other methods of screening. However, it must be realized that many breast cancers that are present in a woman's breast will actually never develop into anything life threatening or even medically compromising. In fact, in some instances if left alone they may eventually disappear altogether. It appears the body has certain natural defense mechanisms that can prevent many cancers from ever reaching their full potential. But when these types of tumors are found on mammograms, they are treated just as aggressively as any other kind of tumor, even though it would not have been necessary to do so. Ductal carcinoma in situ (DCIS) is one example of a type of breast cancer frequently caught by mammograms - but many doctors question whether or not this type of cancer represents much of a danger at all, and doubt that it really needs to be treated in most cases.
Adding more intrigue to the picture, over the years there have actually been some studies performed that appear to show women who have screening mammograms performed regularly in their forties have an increased chance of eventually dying from breast cancer. This has been referred to as the screening paradox, and it is extremely controversial because it has not been found in every study that has tried to look at the question, and as a result many medical experts are convinced this paradox does not really exist. But other doctors have taken the idea seriously, and they have postulated that medical interventions, particularly invasive surgeries, designed to remove cancerous tumors can damage the body's ability to suppress tumors naturally, making some breast cancer patients prone to deadly recurrent cancers in the future.
A final problem with screening mammograms is the false positive. Among women who have screening mammograms performed regularly over a significant period of time, studies have shown that 25-30% will be sent for biopsies to examine a lump found on a mammogram that will turn out to be non-cancerous. The Preventive Services Task Force report placed great emphasis on the stress and psychological strain on women who have gone through this experience, and it was primarily because of the false positive problem they decided to recommend against screening mammograms for women in their forties, as well as a reduced number of mammograms for women between 50 and 75.
Weighing the Evidence
Mammograms, despite how frequently they are promoted as an important tool in the fight against breast cancer, do not necessarily save a lot of lives. This is mainly because the cancers they detect either would not have proven fatal if left alone, or because they would have been found by doctors or women themselves during a physical examination in time to be treated successfully if they had not been discovered on mammograms first.
But the most important thing for women who have breast cancer is to begin treatment before their cancer reaches a stage where it has spread too far to be stopped. In the end, each woman will have to make up her own mind about how often she wants to be checked for the possible presence of breast cancer, and what kind of methods of detection she feels most comfortable using. Even if mammograms do not alter survival odds in a significant way, for many women finding cancers early and treating them aggressively instead of waiting to see what happens will bring a peace of mind that makes regular screening mammograms definitely worth the risks and uncertainties.
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