A new experimental cancer vaccine that targets the immune system has shown some early progress in improving survival in women with metastatic breast or ovarian cancer.

Researchers at the Center for Cancer Research, the National Cancer Institute and the National Institutes of Health tested a vaccine called Panvac in 26 women with breast or ovarian cancer that had spread to other parts of their bodies and had  progressively worsened after chemotherapy. Some weren’t candidates for standard chemotherapy.

“Some patients who had limited tumor burden and  whose immune system was not compromised by multiple rounds of prior chemotherapy seemed to benefit from this vaccine,” wrote the authors, led by Dr. Mahsa Mohebtash at the National Cancer Institute.

Dr. Hatem Soliman, an assistant member of the Moffitt Cancer Center Women’s Oncology and Experimental Therapeutics Departments  in Tampa, Fla., explained that the primary benefit with this type of vaccine is longer survival.

“The vaccine is similar to what we’re seeing in terms of clinical effects from other vaccine studies,” he said.  “What it seems to do is not so great a job at shrinking disease, but offers a survival advantage.”  Soliman was not involved with the Panvac research.

“The  majority of the other patients’ cancer progressed pretty rapidly on the vaccine, but one thing you may see down the line is they may do better with subsequent treatments, or the vaccine may slow down the progression, even if the disease is growing,” he added.

Panvac is a type of vaccine that targets the immune system as a way to treat cancer.  Soliman explained that the vaccine consists of the body’s own cells that have been modified by adding viruses that code for proteins associated with cancer cells.  The body’s own cells will then recognize these cancer-associated proteins and prompt the immune system into attacking them once they are injected back into the body as a vaccine.

Panvac  and other immune-targeting vaccines may be more effective in people who have gone a long time without chemotherapy or haven’t had  much in the past, since chemotherapy tends to weaken the immune system and it may not be able to mount a response to the vaccine.

Soliman and the study authors said this research is encouraging, but the vaccine is still a long way from actually being put to clinical use.

Future research, the authors wrote, should “select patients with less aggressive tumors in the earlier stages of disease.”

Soliman said another promising option is to explore the possibility of combining vaccines with agents that stimulate the immune system.

“It’s an interesting vaccine,” he said. “There’s a lot of work that remains to be done to get the benefit that we would like to see.”