The elevator doors open on the fifth floor at Johns Hopkins Hospital, and Peggy Murphy tentatively steps out, as if crossing a threshold in the struggle to stay ahead of her breast cancer. Last fall, she had been accepted into Dr. Leisha Emens' clinical trial testing an experimental breast cancer vaccine, one designed to teach her immune system to attack the tumors that had spread to her right hip.

She had been euphoric, given at least a chance to help her live-in grandchildren find the right path in life. But by spring, even after receiving four rounds of the vaccine, Murphy's bone scans were lighting up with cancer: in her left hip, her back, her skull.

So on this early July morning, the 57-year-old must leave behind her bold hopes for a cure. She is reverting to a more conventional therapy, one that she knows won't heal her but might give her a little more time. Doctors have recommended intravenous chemotherapy three weeks out of every four, a pattern of treatment that, if she is one of the lucky ones, could go on for years. Today she will have surgery to install a port under the skin in her chest to make it easier for nurses to give her that medicine.

"I'm having a hard time with this one," she says, slumping into a seat in the waiting room. Her clear blue eyes are red from the tears she shed on the ride from near Lancaster, Pa. "It represents the vaccine not working.

"It symbolizes being closer to the end."

She entered the trial certain the vaccine would make her better. Before she signed up, by happenstance she had met two women who were doing so well on the vaccine that their scans didn't detect cancer anymore. No one promised Murphy a cure - the lengthy consent form stated: "It is unlikely that you will be cured of your cancer if you join this study." But when she sees how well some of the others have done, she can't help but feel cheated.

Why didn't it work for her?

Emens has no answers to give Murphy, or any of the other women participating in her trial. Her experiment is not done. At the same time, Emens must keep an eye on a more distant horizon the women may never see: the day when their daughters may get a vaccine to prevent a disease that still kills 40,000 American women each year.

Emens believes she can train the body's immune system to recognize cancer and destroy it. But at this point, her research can only look at whether the vaccine is safe, whether it elicits an immune response and what doses of chemotherapy should be given to rev up the immune system to attack. Emens knew there would be failures on the way there - even in mice, under ideal conditions, only 30 percent were cured of their cancer.

Murphy knows she is one of those failures.

Why didn't it work for her?

Does the vaccine work better in women with certain types of breast cancer? In those whose cancer has spread to their organs but not to their bones? In those who have not had extensive chemotherapy in the past? Did it matter how much chemo they get before and after the vaccine? The women received varying doses. Through the first trial, which the last woman completed this summer, Emens has learned that more chemo isn't always better. Too much, it turns out, may be killing off just what the vaccine is trying to enhance.

As Emens solves some of those mysteries, and each vial of blood taken could yield additional clues, she hopes she is moving closer to developing a vaccine that works better than this one.

For the present, though, Murphy considers herself a casualty. "Tomorrow, I'll be a fighter," she says, her accent revealing a childhood spent on Long Island. "Today, I don't feel like it. Today I'm angry."

A hard life
Murphy has rarely had it easy. An early divorce left her a single mother of two. There have been times when she had to do that all over again, taking in her two grandchildren, ages 6 and 7, when her daughter Tracy Ramirez, now 26, hit some rough patches.

All four of them live together in the two habitable bedrooms of Murphy's split-level duplex. Her daughter is on track for the moment. The family lives off Murphy's Social Security and Ramirez's food stamps. The children are finally learning how to read, now that they aren't switching schools all the time.

Murphy doesn't like to think about what will happen when she is gone.

" Life isn't about waiting for the storm to pass," reads a framed picture on the living room wall. "It's about learning to dance in the rain."

Murphy has spent most of her life in jobs like waitressing, jobs that didn't hold much room for advancement. She considers herself almost lucky that she got sick in the years after she became a postal clerk. The job came with health insurance.