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(NBC NEWS) -- 70 percent of ovarian cancer patients will eventually die from the disease.

The problem is there are no treatments to effectively kill the cancer if it returns, but now doctors say a patient's own immune system can be trained to attack the cancer better than any drug could.

Yi Zuo is an ovarian cancer.

She's had two surgeries and chemotherapy, but it's an experimental cancer vaccine that has helped get her to this point.

"All my tests and scans have shown no sign of recurrence," she says.

Zuo, along 30 other ovarian cancer patients, enrolled in a clinical trial at the University of Pennsylvania that uses a patient's tumor cells to create a personalized vaccine.

This isn't like a flu shot that stops an illness before it strikes, rather it prevents the cancer from coming back.

"This vaccine is made to educate and teach the immune system to identify the cancer cell and hopefully attack it," explains Dr. Lana Kandalaft of the Abramson Cancer Center.

The vaccine is sometimes amplified with an immune system booster made from a patient's own blood.

75 percent of women who got both treatments experienced some benefit.

While researchers are excited about the findings, outside experts say this is just the first step in using the immune system to target ovarian cancer.

"More women will need to be studied and we'll also need a longer follow-up term to see what the side effects are," says Dr. Ursula Matulonis of the Dana-Farber Cancer Institute.

Zuo had no side effects from the vaccine, a welcome change after her experience with chemotherapy.

Patients in the trial were also given the cancer drug Avastin.

Doctors are still trying to parse out which treatment is working to slow the progression of the disease.

The trial is enrolling new patients.

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