SUNDAY, April 13 (HealthDay News) -- A breast cancer vaccine significantly reduced the risk of recurrence for patients who have a high expression of the protein HER2-neu.

This type of breast cancer, representing about one-quarter of all cases, tends to be deadlier than other forms of the disease. In this group, the vaccine reduced mortality by 50 percent.

Even better, however, the vaccine lowered mortality by 100 percent in women with breast cancer and low or intermediate expression of HER2/neu. Currently, these women have no therapies other than conventional cancer treatments such as surgery and chemo.

"We now have something we think works in the majority of women with breast cancer who are currently underserved," said Dr. George Peoples, senior author of the study, which is expected to be presented at the American Association for Cancer Research annual meeting, in San Diego. "It's also very, very well-tolerated, like a flu shot."

Peoples is chief of surgical oncology at Brooke Army Medical Center in San Antonio and director of the Cancer Vaccine Development Program at the U.S. Military Cancer Institute.

According to study lead author, Dr. Linda Benavides, a resident in general surgery at Brooke Army Medical Center, the biotech firm, Apthera, has licensed the vaccine, named it NeuVax, and is currently planning phase 3 clinical trials.

But there's still no guarantee the vaccine will reach the market.

"It is a very exciting area of research, but it's very exploratory and not ready for prime time," said Dr. Minetta Liu, a translational researcher/breast oncologist at Georgetown's Lombardi Comprehensive Cancer Center.

Other cancer vaccines have been tested, mostly to treat tumors that have already spread, with little success.

"We've been studying vaccines in the setting of metastatic cancer, but the immune system has already been effective, and the cat's out of the bag already," Liu said. "Many of us believe the time to get rid of them is as they're developing. It's just so hard to study it in that setting."

This vaccine (also known as E75), which stimulates the immune system to recognize the cancer as foreign, aims to prevent a recurrence in women who have already had one round of cancer. It is the furthest along of all the cancer vaccines.

This trial involved 165 breast cancer patients with HER2/neu tumors and lymph node involvement; 94 were vaccinated (initial shot plus boosters) and 71 served as controls.

Immunity was raised in all women who received the vaccine, but the biggest benefit was seen in those women with low and intermediate expression of HER2/neu or those who are not eligible for Herceptin, the drug currently used to treat this type of cancer.

After a follow-up of about 30 months, recurrence rates were similar between high overexpressors in both the vaccine and control groups (18.2. percent and 13.8 percent, respectively). But, there was a greater than 50 percent reduction in mortality rates.

In those with low or intermediate expression of the protein, results were more startling. Less than 11 percent of low HER2/neu expressors had a recurrence, versus 18.2 percent in the control group. The mortality rate in the vaccine group was zero, compared with 38 percent in the control group.

More information

Visit the National Cancer Institute for more on breast cancer.