CAMBRIDGE, Mass. — Two of the key vaccines against cervical cancer have succeeded in boosting an already-potent natural immune response without needing boosters.
The cancer vaccines now work best against pre-cancerous cells or cancer cells that have already spread to other parts of the body, according to data presented at the annual meeting of the American Association for Cancer Research on Monday.
“Cervical cancer vaccines have shown great promise,” said Mark Metzger, a researcher at the Dana-Farber Cancer Institute and Harvard Medical School who was a key author of the new study.
“We were surprised we could improve immune response to pre-cancerous cervical cells and non-cancer cells without boosting antibodies,” Metzger said. “We were even surprised with the amount of benefit.”
The trials conducted by researchers at the National Cancer Institute and a sister institute at Harvard led to new testing of the vaccines designed to hit specific targets rather than stimulate all the immune system’s resources, Metzger explained.
Another of the researchers, Patricia Graeser at Harvard, said the trial supported the idea that the vaccines may work better when given prior to an already-occurring cancerous cell rather than decades after its first appearance.
“You can hit pre-cancerous cells with the vaccine, and the cell is destroyed and it’s removed from the tumor,” Graeser said. “Also, immune cells can actually activate as part of the immune response and help combat cancer cells.”
Immune problems such as persistent fever were also observed with vaccines in the past, she noted.
Early data collected on two vaccines, Cervarix from GlaxoSmithKline and Gardasil from Merck, suggested the vaccines stimulated the immune system to treat cancer.
But a 2008 paper in the journal Cancer Immunology also indicated that the vaccines needed a booster shot to engage the immune system to fight disease. Metzger and Graeser are part of that research.
Now, they plan to look at a combination of the two vaccines to see whether the side effects of Gardasil and Cervarix—including fever, rash and decreased immunity—are worse together.
Metzger said one recent study in mice, published last month in the journal Nature Immunology, showed that antibodies expressed on the surface of the immune system after Gardasil or Cervarix can actually switch off other immunologic cells.
Gardasil and Cervarix both have had market approval in women worldwide for the past five years and the benefit seen by many patients seems to warrant more scrutiny on their combined use, Metzger said.
More than 94,000 cases of cervical cancer are diagnosed each year in the United States, according to the American Cancer Society. About 4,700 women are expected to die of the disease this year, which can be easily prevented with early detection and preventative measures such as screening and pap smears.
There is still much to learn about the therapies, and other researchers and manufacturers will be taking the new data into account as they plan their next vaccine trials, Metzger said.
More than 75 percent of women eligible for the initial study in Cervarix and Gardasil experienced disease-free periods for more than 12 months after vaccination.
Cervarix has been approved in some 70 countries, while Gardasil has been used in more than 73 countries.