Ovarian Cancer Vaccine Might Extend Survival

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Although most women with advanced-stage ovarian cancer do respond to chemotherapy, 70 percent still die of the disease within five years of diagnosis.

Researchers are exploring vaccines as one way to extend remission. Vaccines essentially harness the body's own immune system to recognize some component of the cancer, then turn the body's forces against it.

Immune agents called cancer-testis antigens are found in abundance in a variety of cancer types and so are good candidates for vaccination, the researchers explained. An antigen known as NY-ESO-1 has shown particular promise.

"NY-ESO-1 peptide has been recognized and known as a potentially tumor-specific antigen, and that's the one single peptide that they're using for this particular vaccine," Morgan explained.

The Roswell Park team tested the vaccine in 18 women with epithelial ovarian cancer, which originates in the covering of the ovaries. All participants had undergone surgery and had completed chemotherapy. Most of the patients had advanced disease.

The vaccine turned out to be safe and also induced patients' antibody and T-cell responses, both measures of immune responses. The T-cells were able to recognize tumor cells containing NY-ESO-1.

Vaccine-induced immune cells were also found to be present in patients up to a year after immunization.

One woman experienced a complete regression of her disease after 10 vaccinations, although the disease did recur again eight months after the vaccinations were discontinued.

While phase I trials like this one are intended mainly to look at safety issues, they can often yield more information, Morgan said.

"While the classical goal of phase I trials is toxicity evaluation, these kinds of agents are different, because they usually don't have much in the area of toxicity," he explained. "What you're really looking for is a response to the proteins."

"I'm very encouraged," he continued.

Fishman said the findings are promising, but even better vaccine candidates may lie ahead.

NY-ESO-1 "is probably not the best peptide to be used as a vaccine because all vaccines are based on targeting something unique to the disease, and this is not unique to ovarian cancer," Fishman said.

However, the study "does show the promise of immunotherapy," he added, "and as we become more sophisticated, hopefully someday we will be able to have vaccines that will treat or ultimately prevent one from developing cancer. That is the goal -- to vaccinate so you never get the disease."

More information

There's more on ovarian cancer at the U.S. National Cancer Institute.