A human T cellWIKIMEDIA, NIAID, NIHOvarian cancer is a particularly hard-to-treat disease. It’s often diagnosed late, and even after surgery and chemotherapy, around 85 percent of patients relapse and develop chemoresistance. But a preliminary clinical trial, carried out by researchers at the University of Pennsylvania, has shown promising results for a new type of vaccine that aims to boost patients’ immune systems to fight the disease. The findings were published yesterday (April 11) in Science Translational Medicine.

“This vaccine appears to be safe for patients, and elicits a broad anti-tumor immunity,” study coauthor Janos Tanyi of the University of Pennsylvania’s Perelman School of Medicine says in a statement. “We think it warrants further testing in larger clinical trials.”

The researchers focused on patients with recurrent advanced epithelial ovarian cancer, which has a five-year survival rate of around 17 percent. First, the team extracted dendritic cells—antigen-presenting cells that help prime T-cell responses—from each patient, and grew them in the presence of antigens from that same patient’s tumor. Then, they injected the dendritic cells back into the patient’s lymph nodes to trigger an antitumor T-cell response.

In the trial, all 25 patients received a series of such injections, either alone or in combination with chemotherapy drugs. None of the vaccinated patients reported severe side-effects, and patients who received the vaccine along with two chemotherapy drugs had a two-year survival rate of 78 percent—compared with just 44 percent for patients in a control cohort receiving only chemotherapy. Tanyi tells the Los Angeles Times that the vaccine appears to be “so safe it’s unbelievable.”

Otis Brawley, chief medical officer of the American Cancer Society tells CNN that the study “clearly justifies a larger clinical trial.” But he also cautioned against overstating the promise of the team’s personalized approach compared to tried-and-tested treatments. The public “often wants to pass up better-proven conventional therapy for an unknown in immunotherapy,” he says.