A vaccine that coaxes the body to attack tumor cells has shown promise in a small study of advanced breast and ovarian cancer patients, improving overall survival times and stopping the disease for a handful of breast cancer patients.
The PANVAC vaccine, administered to 26 women through monthly shots, helped the body's immune system recognize proteins produced specifically by cancer cells, said study author James L. Gulley, MD, PhD, director of the clinical trials group and deputy laboratory chief at the Laboratory of Tumor Immunology and Biology at the US National Cancer Institute.
All of the women had breast or ovarian cancer that had spread to other organs and were considered "heavily pre-treated with other therapies, with 21 having received at least three chemotherapy regimens. In addition to the four breast cancer patients whose disease stopped progressing, one woman with breast cancer experienced a "complete response, meaning her cancer disappeared.
Among the 12 study participants with breast cancer, the median time before the disease continued to progress was 25 months and the median overall survival was 13.7 months. For the 14 patients with ovarian cancer, the median time to progression was two months and the median overall survival was 15 months.
Side effects from the vaccine were exceedingly mild, with minor injection-site reactions the most common problem reported.
The study was published in the journal Clinical Cancer Research
Previous Colorectal Cancer Study Findings
The PANVAC vaccine, containing certain genes that encourage the immune system to recognize and destroy tumor cells, was previously studied in 70 patients with advanced colorectal cancer, Dr. Gulley said. While the time before disease progression was similar between patients who did and did not receive the vaccine, the overall survival time in the vaccine group was "strikingly better," he noted.
"Anytime we have one type of biologic treatment demonstrate some success, it's exciting." said Elizabeth Poynor, MD, a gynecologic oncologist and pelvic surgeon at Lenox Hill Hospital in New York City, who was not involved in the study. "No matter how small the study is and early studies will be small-when we have positive results on a particular technique, it's a very hopeful thing. These are our most difficult patients to treat; they have failed multiple therapies."
Indeed, most participants-whose average age was 57-had exhausted other forms of treatment, Dr. Gulley said, which likely hampered their immune systems from responding as fully to the vaccine as they otherwise might have. As therapeutic vaccines become more established, Dr. Gulley said they might prove even more effective in patients whose disease is less advanced.
"That's exactly what I'd like to eventually see-the vaccine used earlier in the disease process before other (toxic drugs that can damage the immune system," he said. "I think it makes more sense, when the immune system is more likely to overcome a lower tumor burden. Until recently we haven't seen a lot of substantial clinical impact of vaccines."
"This is an exciting step forward," said David Fishman, MD, a professor of obstetrics, gynecology and reproductive science at Mount Sinai Medical Center in New York City. "The ultimate goal would be to identify unique proteins in an individual patient's cancer and use vaccines unique to that patient."