For that reason, it's not clear yet whether the vaccine could supplant colonoscopies altogether in high-risk patients, says Mack Ruffin IV, professor of family medicine and a research scientist in epidemiology at the University of Michigan, who is not involved in the trials. "If they still need colonoscopies, we haven't done anything but add extra cost and side effects to managing people with polyps."

The Pitt investigators have been recruiting subjects for the trial since October 2008, and they expect to finish gathering data in fall 2011. Patients receive an initial dose of the vaccine with boosters 2 and 10 weeks later, and their immune response is monitored for a year. Because their history of advanced adenomas puts them at high risk for cancer, the patients are monitored throughout the trial with colonoscopies--the current gold standard for surveillance--giving the researchers a preliminary idea of whether the vaccine can limit recurrence or progression.

So far, in the more than 20 subjects already enrolled, says Schoen, "the vaccine is extremely well tolerated." Beyond some redness and soreness at the injection site and the occasional short-term fever, there have been no adverse effects. The next step, Schoen says, will be another trial to determine more precisely the relationship between vaccine administration and adenoma recurrence. He estimates that those experiments could begin within two years.

Abnormal MUC1 isn't limited to colorectal cancer. It's also present in some other cancers, including most breast tumors, meaning the new vaccine could be adapted for other uses. More broadly, the strategy of stimulating the immune system to attack a tumor-related protein may be relevant for other types of cancer as well. Many proteins are known to be aberrantly expressed in malignant tissue, says Schoen, and "vaccines against other proteins could be used for other cancers."