The dramatic drop in the rate of the most common form of breast cancer is very good news, but not good enough to proclaim that the battle against this disease is over. The 15 percent decline in diagnoses from August 2002 to December 2003 is but one step among many in understanding mitigating factors in certain forms of cancer.
If anything, the news is a tribute to the type of research and data collection that rarely receives the attention it deserves. The new analysis of breast cancer rates by researchers from the M. D. Anderson Cancer Center in Houston was based on compilations by the National Cancer Institute showing cancer incidence -- the kind of careful statistical recording that paves the way for insights.
For women of all ages and all breast cancer types, the incidence of the cancer dropped by 7 percent in 2003, or about 14,000 cases, according to the researchers. Such a significant drop had not occurred in quite a long time; cancer rates had been increasing slowly since 1945. Incidents of so-called estrogen positive tumors, which account for 70 percent of all breast cancers, showed the most striking change.
Researchers believe the reason behind this mystery may lie in a single fact: Millions of women abandoned hormone treatment for symptoms of menopause after a large national study concluded that the hormones slightly increased breast-cancer risk.
Hormone use dates back 25 years, when some circumstantial evidence showed that in addition to relieving menopause symptoms, hormone replacement therapy substantially reduced the rate of heart disease. But there never was a comprehensive study proving that theory. A large-scale study, the Women's Health Initiative, began years later in the 1990s.
That randomized clinical trial, in which half the women took estrogen and half took a placebo, showed that patients using a combination of estrogen and progesterone incurred a slight increase in the risk of breast cancer and a slight increase in the rate of heart disease as well.
Western New York women, recruited to the study through the University at Buffalo, played a valuable role in this evaluation of hormone therapy. Dr. Stephen Edge, chairman of the breast and soft tissue surgery department at Roswell Park Cancer Institute, said the study allows rational judgments to be made about treatments, and may make a difference in cancer rates.
While researchers haven't yet proven the drop in breast cancer rates is due to the discontinuation of hormone treatments, it's a very plausible explanation. It appears that hormone-use warnings were heeded, and saved many women from suffering or death.