Early Results Promising for Breast Cancer Vaccine

May 16, 2012— -- A vaccine may be able to keep an aggressive type of breast cancer from returning in women who have a history of the disease, according to early results of a new study. The vaccine still needs further research, but breast cancer experts say the results are promising.

Researchers at the MD Anderson Cancer Center in Houston developed a vaccine, called AE37, that trains the body's immune system to attack a common piece found on breast cancer tumors, a protein called HER2, which helps tumors grow.

"With this vaccine, we've educated the immune system to recognize this protein, HER2," said Dr. Elizabeth Mittendorf, the lead investigator on the trial. "If some rogue tumor cell is floating around, it can recognize it and take care of it before it can settle into bone or other parts of the body."

About 25 percent of breast cancer cases have an overactive amount of the HER2 protein, called HER2-positive breast cancer. This form of breast cancer is usually more aggressive and harder to treat than other types. But most tumors usually have some level of the protein, even if the amount is not enough to be classified as HER2-positive.

Mittendorf said one of the most encouraging things about the vaccine is that it seemed to reduce the risk of recurrent breast cancer in women who had both high and low levels of HER2, a group that accounts for about 70 percent of all breast cancer cases.

Mittendorf and her team studied 201 patients who had a history of breast cancer but who were disease free at the time, giving the vaccine to about half of them. Based on the early outcomes of patients in the trial, the researchers projected that breast cancer would come back for 10.3 percent of the women who got the vaccine compared with 18 percent of the women who had not been vaccinated. That translates to a 43 percent reduced risk of recurrent breast cancer.

The study's results will be presented next month at a meeting of the American Society of Clinical Oncology.

Dr. Michele Zembo, 57, was one of the patients who got the vaccine. The pediatric orthopedic surgeon from New Orleans was diagnosed with breast cancer in October 2010 and after a year of chemotherapy, a mastectomy, radiation therapy and reconstructive surgery, she knew that her battle with breast cancer may not be over.

"That's just a reality of breast cancer. Somewhere down the line, there is that risk that it will come back," she said. "So you start wondering, what can I do to reduce my risk?"

She got regular exercise, changed her diet and even changed her high blood pressure medication when new evidence suggested beta blockers might reduce the risk of breast cancer. When her doctor told her about the clinical trial testing the AE37 vaccine, she did her research and decided to join the study.

Zembo said she experienced almost no side effects of the vaccine, just a minor rash and pain where the shots of the vaccine were injected. So far, Zembo said she is still free of breast cancer.

"I've tried to do everything that I can do to try to decrease my risk of recurrence. To me, this vaccine is one additional step, and a big step, that does that," Zembo said.

Breast cancer experts said the results of the study so far are promising, but they were cautiously optimistic. The number of patients in the study was relatively small, and they were monitored for less than a year. Women who have had breast cancer are at risk for recurrences for many years after their first diagnosis.

"We've seen a lot of treatments that have very early promise, but with follow-up studies just don't pan out, said Dr. Jay Brooks, chair of hematology and oncology at Ochsner Health System in New Orleans. "But it's interesting and something I would love to use in my practice if it proved successful."

The study is ongoing, and Mittendorf said it should finish in the fall of 2012. She hopes to launch a larger trial for the vaccine after that.

Scientists have been pursuing the idea of treating cancer with a vaccine, a method that would mean a more targeted, less toxic approach to treating the disease. Provenge, a vaccine for treating prostate cancer, was the first cancer vaccine approved by the U.S. Food and Drug Administration, getting the agency's nod in 2010. The development of other vaccines for melanoma and lung cancer are also under way.

Other vaccines for breast cancer have been attempted, and some have targeted the HER2 protein. But experts say the results in the current study are more encouraging than most.

"It is exciting to imagine that a vaccine could prevent recurrence of breast cancer," said Dr. Harold Burstein, a breast cancer specialist at Dana Farber Cancer Institute in Boston. "These are provocative data that will hopefully generate enthusiasm for a definitive, large trial to assess this vaccine."

Mittendorf said the vaccine isn't useful for treating patients with advanced forms of the disease and isn't intended to replace other forms of treatment but to work in conjunction with them to fight breast cancer.

"We've gotten pretty good at taking care of breast cancer, but even as good as we are now there are still patients who recur and succumb to disease," she said. "Any tools we can use to prevent that from happening we should use."

ABC News' Dr. Ruby Shandilya contributed to this report.