You're referring to the findings of a very large study in China, which showed that breast self-examinations don't reduce deaths from breast cancer. The study was conducted in Shanghai from 1989 to 2000 by a team that included researchers from China and Norway, as well as from Seattle's Fred Hutchinson Cancer Research Center.
More than 266,000 women participated. Half were taught how to do breast self-exams and were monitored regularly; the other half received only routine medical care. After 10 years, results showed no fewer breast cancer deaths among those who did self-exams.
The Shanghai study wasn't the first to cast doubt on the assumption that breast self-exams save lives. Another large trial, conducted in St. Petersburg, Russia, followed 122,471 women between the ages of 40 and 64, half of whom were taught to do self-exams. After five years, almost half the women in the self-exam group had stopped checking their breasts. After nine years, both groups had the same rate of breast cancer deaths.
Breast self-exams have another downside: the women in both studies who did self-exams had higher rates of benign breast biopsies than those who didn't.
Despite these discouraging findings, many experts in this country still encourage women to examine their breasts once a month. As you may know, mammography, the other method we have to detect breast cancer, is also flawed. It misses up to 30 percent of breast cancers and may not even show lumps women can feel.
You may not find a tiny cancer by examining your breasts but knowing how they normally feel enables you to recognize changes that might be significant. The tools we have for diagnosing early breast cancer are imperfect, but until something better comes along, it makes sense to take advantage of them all: breast self-exam, an annual breast exam by your physician and regular mammograms.
Dr. Andrew Weil