WASHINGTON - US scientists have developed an experimental vaccine against advanced ovarian cancer that triggers anti-tumor immune responses using cells made from patients' own tumor.

The vaccine provoked a positive response in 61 percent of woman with stage 3 or 4 ovarian cancer, according to a report presented Saturday at the American Association for Cancer Research annual meeting in Washington.

The University of Pennsylvania researchers first isolated immune cells called dendritic cells from patient's blood. They then created individualized vaccines by exposing each patient's dendritic cells to her own tumor tissue that had been collected during surgery.

They found 19 out of 31 patients clinical benefit after vaccine treatment and developed an antitumor immune response.

Of these 19 patients, eight had no measurable disease at the end of the study and remained on maintenance vaccine therapy. One patient of the eight patients remained disease-free for 42 months following vaccine treatment, they said.

While vaccination therapy alone showed about a 61-percent clinical benefit, said lead author Lana Kandalaft, the combination of both therapies showed about a 75-percent benefit.

Both treatments were given in conjunction with bevacizumab, a drug that controls blood vessel growth.

"We offer patients with ovarian cancer a potential therapy with minor side effects and a good quality of life," Kandalaft said.

The researchers said they will continue to work to improve the vaccine platform to further enhance its efficacy.