Breast Cancer Screening
Has routine screening led to a decrease in breast cancer mortality?
After the increase in routine examination of the breasts (annually by a doctor or monthly by the woman herself), the rate of detection of breast cancers crept up by just under two percent per year during the 1970s. The overall death rate from breast cancer remained the same in 1980 as it had been in 1970 or 1960 or 1950. This combination -- increased detection but similar death rates -- means that more women know about their illness for a longer period of time, but women still die from the disease at the same rate.
Why hasn't early detection decreased the number of breast cancer deaths?
Breast cancer is a disease of the body, not just of the breast. As medical researchers in the 1970s and 1980s discovered a great deal more about how breast cancer develops and progresses, their perceptions of the disease changed. The older understanding of the disease was that a tiny tumor became medium-sized, then large, then spread to the lymph nodes in the armpits, and finally entered the bloodstream to spread (metastasize) to other parts of the body where it became a life-threatening illness. This conception explains why the earlier recommended treatment for breast cancer was a total or radical mastectomy, the removal of the breast and lymph nodes and possibly the surrounding muscles. This treatment was believed to interfere with the final stage of breast cancer—the spreading of cancerous cells from the lymph nodes into the bloodstream.
The new understanding of breast cancer is that it is a systemic disease: any cancer large enough to feel is one that may have spread into the bloodstream already, whether the cancer is large or small, and whether it can be found in the lymph nodes or not. A woman's immune system may have inactivated any early cancer cells that escaped into the blood, or else the cells may have evaded (or outnumbered) the immune defenses. This is why systemic therapy (also called adjuvant or whole-body therapy) is now recommended in most cases of breast cancer, even when the diagnosed cancers are small.
A treatment choice of lumpectomy instead of mastectomy makes no difference, since the most effective treatment is one directed to the entire body (hormone therapy such as tamoxifen, or other types of chemotherapy).
