When Betsy Lambert, a New York lawyer, was told she had breast cancer two years ago, her surgeon advised her to have a lumpectomy, removing only the tumor from her breast, followed by six weeks of radiation treatment.
But Ms. Lambert, terrified by the disease, sought two more opinions, one from another surgeon and another from a radiologist. Both urged her to have a mastectomy, removing the entire breast.
"I really agonized," she said. "It was a very, very scary time." In her heart, she said, she believed "a mastectomy is symbolic of the removal not just of the breast but of the disease."
She read the medical literature and she forced herself to accept what the studies said: that in cases like hers and in the vast majority of cases, there is no medical advantage to having a mastectomy. And, in the end, she chose a lumpectomy.
But cancer researchers say Ms. Lambert is the exception.
Most American women with breast cancer have mastectomies, to the puzzlement of researchers who point out that large, highly regarded studies have shown that there is rarely any medical reason for amputating a breast rather than simply removing the tumor and treating the breast with a short course of radiation.
Even most women with large tumors are just as well off with a lumpectomy as with a mastectomy, studies show.
Seven studies involving thousands of women who have been followed for as many as 15 years after their cancer surgery have failed to find any difference in survival when women with small- to moderate-size tumors had lumpectomies and radiation rather than mastectomy.
Recent studies indicate that even women with very large tumors, for whom a lumpectomy might mean removing virtually all of the breast, can often shrink their tumors down to virtually nothing with chemotherapy and then have a lumpectomy.
The National Cancer Institute endorses lumpectomies for women with stage I and II breast cancer, in which the tumor is less than 2 inches in diameter, or 5 centimeters. A great majority of breast cancer patients fall into this category.
So, cancer experts ask, why does the more mutilating and expensive operation remain so popular?
The question, experts say, reveals an often overlooked aspect of medical practice. It shows that data themselves may not be enough to force a change in medical practice, even when the statistics are unquestioned by medical experts.
"The observation is unequivocally clear-cut," said Dr. I. Craig Henderson, who directs breast cancer research at the University of California in San Francisco's Cancer Center. "Doctors and patients are not immediately affected by clinical trials."
Some doctors say it is their colleagues who urge the unneeded mastectomies on women. But they say there is no obvious reason for this because the data from the clinical trials have been widely publicized.
They speculate that doctors may have psychological difficulty letting go of the methods and philosophy of treatment that they learned in medical school, that some may be influenced by the extra money they receive for a mastectomy or that the doctors believe that women will be happier with their breasts removed.