In what researchers are hailing as breakthrough, scientists at the University of Pittsburgh are reporting a new first-of-its-kind vaccine has proven to be a successful new weapon in the prevention of colon cancer.
In clinical trials involving patients at high risk of developing the disease, the Pitt vaccine was shown to boost the body’s natural immune defenses to target early signs of colon cancer and prevent its growth.
The study, published online in the journal Cancer Prevention Research, was funded in part by the National Cancer Institute and the National Institutes of Health.
“This prophylactic colon cancer vaccine boosts the patient’s natural immune surveillance, which potentially could lead to the elimination of premalignant lesions before their progression to cancer,” said Olivera Finn, head of the Department of Immunology at Pitt’s School of Medicine and the vaccine’s developer, in a university press release.
“This might spare patients the risk and inconvenience of repeated invasive surveillance tests, such as colonoscopy, that currently are used to spot and remove precancerous polyps.”
Colorectal cancer is the third-leading cause of cancer death in the United States, causing nearly 52,000 deaths annually. The American Cancer Society estimates more than 103,000 new cases of colon cancer and 40,000 cases of rectal cancer are diagnosed each year.
Colon cancer takes years to develop. The first signs are often intestinal growths, called polyps, that are usually benign. Polyps that can become cancerous are called adenomas and typically are removed before cancer develops.
The Pitt study involved people with a history of an advanced adenoma, which puts them at higher risk for subsequent colorectal cancer.
“Around 30 to 40 percent of these patients will develop a new polyp within three years,” said Robert E. Schoen, M.D., professor of medicine and epidemiology with Pitt’s Division of Gastroenterology, Hepatology and Nutrition, and clinical leader of the study. “In this study, we demonstrated the ability of the vaccine to boost immunity. Subsequent trials need to evaluate the vaccine for its ability to lower or prevent polyp recurrence and thus progression to colon cancer.”
The Pitt vaccine targets a protein called MUC1, which is altered and produced in excess in adenomas and cancer. Because MUC1 also is abnormally present in pancreatic, breast, lung and prostate cancer, researchers plan to test the new vaccine’s effectiveness in preventing those cancers, as well.
The vaccine was tested in 39 cancer-free patients, ages 40 to 70, with a history of advanced adenomas. Patients were given an initial dose of the vaccine and then additional shots two and 10 weeks later. Blood samples were drawn to measure immune response at various times during the trial, up to a year after it started, when a booster shot was also administered.
The results showed the vaccine produced a strong immune-system response in 17 of the patients (44 percent). Researchers said the lack of response in the other patients was likely due to already high levels of cells that suppress the immune system’s ability to fight cancer.
“This suggests that it might be better to vaccinate people against colon cancer at an even earlier stage, or vaccinate only people who do not already have suppressed immune systems,” said Finn.
The vaccine produced only minor side effects, including red skin and discomfort at the injection site and flu-like symptoms after the first injection.
If additional tests confirm the vaccine’s safety and effectiveness, it could become the first vaccine based on tumor cell proteins to prevent cancer.