She was a healthy, health-conscious woman nearing her 40th birthday when she went in to have her first mammogram . As a nurse at the university hospital in Seattle, Becki Swearingen knew all about the benefits of screening for breast cancer.

But she wasn't prepared for the results.

The radiologist telephoned to say that there was "a suspicious area in one breast." An abnormality on the test. She was told to come in for a second mammogram.

"My response ranged from denial to near panic," she says. "Is this the first phase of a life-changing illness for me? I tried to be optimistic."

Swearingen, like thousands of women, got on the train of medical testing where one scan leads to another test that leads to procedure that leads to another test and another procedure -- clackity-clack down the health care track.

When you get on the testing train, you don't know where it is going, how long the journey will take, where you will end up. With each stop -- each test -- you get deeper into the heart of medical darkness, deeper into your own fears that the train is headed toward your own mortality.

Swearingen's second mammogram was not routine. It involved more films. And another ominous report. There was still a suspicious area. The next stop: an ultrasound test and then the radiologist said the word, "biopsy."

"I was feeling overwhelmed by events," Swearingen says. She was referred to a surgeon. "My imagination became more difficult to control," she explains. "I started to visualize myself as a cancer patient, to question my mortality -- am I the kind of person I want to be?"

The biopsy was uncomfortable, but she told herself it was nothing compared with the pain she had seen breast cancer patients endure.

The next day the radiologist called with the good news: It wasn't cancer. It was nothing. An "architectural distortion," the doctors called it.

Whew! A wave of relief. Swearingen felt she had dodged the bullet.

But a month had gone by from the first mammogram to the biopsy, a month on the medical train going slowly from one test to the next, a month suspended from normal life.

Something is wrong with breast cancer screening in this country. A month of anxiety is a terrible toll that medicine too often exacts on women who want to take advantage of the proven benefits of breast cancer screening.

A new study suggests that Swearingen's experience is fairly typical. About half of women who undergo regular breast cancer screening tests over a decade will receive a "false positive" result, meaning the test shows the possible presence of a tumor that on further testing turns out not to be there.

Since regular breast cancer screening is an icon of preventive medicine, thousands of women across the country are paying the anxiety price of this technology -- a veritable epidemic of false-positive anxiety. In a previous study, Karyn Lerman of Georgetown University Medical Center found that more than one-third of women who had a false positive test reported significant distress from a deep and persistent fear of breast cancer even six months after the experience.

The anxiety toll can be reduced. To begin with, the technology can be improved to increase detection and reduce the rate of false positives. Radiologists can also be better trained to read the films. Other countries do not tolerate such a high rate of false positive tests.

The health care system and the way women are informed can also be improved. No woman should receive an alarming letter in the mail with news that she has "a suspicious area" in a breast with no explanation or guidance about what the test result means. Ideally, this information should be delivered by the woman's primary physician. Anecdotes abound. One woman called her family doctor in panic on a Friday afternoon: She'd just received the letter, the radiology lab was closed for the weekend, she was terrified she had cancer.

There is also no reason women have to wait weeks and months for follow-up tests. In most cases, a definitive answer can be -- and should be -- obtained within days.

Finally women have to be counseled about the risks of getting a false positive result before undergoing the screening test. "If you have an abnormality {on a screening test}, the chances of your having a cancer is low," says internist Joann G. Elmore of the University of Washington, who conducted the study. Overall, more than 90 percent of women who get a positive test do not have cancer, she notes.

Medical experts are so convinced of the benefits of "catching cancer early" through mammography that they tend to minimize the impact of false-positive anxiety and unwittingly exacerbate women's fear of getting breast cancer. It's a terrible, common disease with more than 43,000 deaths every year. But many women overestimate their risk of breast cancer.

The tragedy of false-positive anxiety is that it might discourage women from getting their breasts examined at all. "They might decide they don't want to relive the experience and avoid screening in the future," says Lerman.

It comes down to this: Who is in control of the medical train -- the technology, the experts or the consumers? The report on false positive results sounds the alarm that for many women regular breast cancer screening is a runaway train.