A new vaccine is being tried clinically to combat tumor cells in a small study of advanced breast and ovarian cancer patients. The results show that there is improvement in overall survival times and stopping the disease for a handful of breast cancer patients.
Researchers at the Center for Cancer Research, the National Cancer Institute and the National Institutes of Health used the PANVAC vaccine. It was administered to 26 women through monthly shots, helped the body's immune system recognize proteins produced specifically by cancer cells, said study author Dr. James Gulley, director and deputy chief of the clinical trials group at the Laboratory of Tumor Immunology and Biology at the U.S. National Cancer Institute.
The team of researchers explained that 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.
The study is published Nov. 8 in the journal Clinical Cancer Research.
Dr. Elizabeth Poynor, a gynecologic oncologist and pelvic surgeon at Lenox Hill Hospital in New York City, who was not involved in the study said, “Anytime we have one type of biologic treatment demonstrate some success, it's exciting…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.”
As therapeutic vaccines become more established, 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…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…I think this gives us a better level of confidence.”
Results showed that among the 12 study participants with breast cancer, the median time before the disease continued to progress was 2.5 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. Two patients had musculoskeletal pain. One had anemia. Some got fevers, he says, which were relieved with fever reducers.
“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. 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.
Gulley explained that the 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. 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. The vaccine targets two proteins, mucin-1 (MUC-1) and carcinoembryonic antigen (CEA), Gulley says. Both are over-expressed in many cancer cells. “The vaccine is designed to have your body's immune system recognize and attack tumor cells making CEA and MUC-1,” Gulley explained.
“This is an exciting step forward,” said Dr. David Fishman, 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.”
“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. “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.”
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