Can You Catch Cancer?
New research shows you can. Here’s what you should know before you talk with your doctor.
Persistence Pays Off
In the early ’70s, dr. Harald zur Hausen announced a radical idea at a scientific conference in Key Biscayne, Fla.: Human papillomavirus (HPV), which can cause genital warts, was the culprit behind cervical cancer. No one believed him. But zur Hausen, now an emeritus professor at the German Cancer Research Centre in Heidelberg, was on a mission to get to the bottom of the disease, which kills almost 300,000 women annually around the world. “I was convinced I was on the right track, although I knew it would require a lot of additional work to prove it.” There were many strains of HPV-some relatively harmless and others quite dangerous-so it was only after the molecular analysis of thousands of warts that a breakthrough came, in 1984. That’s when zur Hausen realized that just two strains of the virus-HPV 16 and 18-were found in 70 percent of cervical cancers.
At the end of 2006, a vaccine was approved in 49 countries, including Canada. Since HPV is transmitted sexually, the ideal time for girls to get the vaccine is before they become sexually active. So far, more than 40 million doses of the vaccine have been distributed worldwide. Cervical cancer is slow-growing, and it will take years before the full benefit of the vaccine is known. However, a February 2010 study of more than 17,000 women in Bogotá showed that getting the vaccine reduced the number of cervical abnormalities related to HPV 16 and 18 by more than 90 percent. In 2008, zur Hausen received Canada’s Gairdner Award and the Nobel Prize for his work.
An Unusual Cocktail
In 1984, in Perth, Australia, Dr. Barry Marshall stood in his laboratory, wearing his white lab coat, said, “Cheers,” then downed a glassful of clear liquid. No ordinary cocktail, this drink contained 100 million Helicobacter pylori (H. pylori) bacteria. Marshall was convinced H. pylori caused gastritis, an inflammation of the stomach lining, as well as stomach ulcers and, eventually, stomach cancer. But he had become frustrated with his in- ability to convince the medical establishment, who believed gastritis and ulcers were caused by stress and dietary factors, that this was true.
“I was a bit nervous; I was drinking pure bacteria,” Marshall recalls. “It’s like eating a strange food, swallowing a raw egg or a goldfish. It took a bit of willpower to get it down.” As he had predicted, Marshall got gastritis. Then he cured himself with antibiotics.
Ten years later, the U.S. National Institutes of Health approved antibiotics as the standard cure for ulcers, and the World Health Organization declared H. pylori a carcinogen. Before Marshall swallowed his unusual drink, no one knew how to ward off stomach cancer. Now we’re learning how. Aklavik, a small community of roughly 600 in the Northwest Territories, has had exceptionally high stomach-cancer rates for years-men here develop it at about three times the national average.
Billy Archie had always worried about the disease, so in 2004, when he became mayor of Aklavik, he decided to do something. He got the Aklavik Health Committee up and running to address his concerns, and in February 2008, a team of 25 doctors, nurses and support staff flew to Aklavik to launch a long-term research project about H. pylori. As with infections from other carcinogens, infection from H. pylori often goes undetected. Scientists think it’s probably picked up from ingesting infected food or water, or from kissing an infected person. Either a breath test or an internal scope can reveal the presence of the bacteria. In Aklavik, more than 200 people tested positive for the bug and were offered treatment with antibiotics. This gave the researchers an idea of just how common the infection was in the area, but left other questions un- answered. For example, which medications would prove most effective in the long run? Is there a way to ensure people won’t be reinfected once cured? Will treatments have any effect in patients who have precancerous gastric lesions?
Karen Goodman, an epidemiologist and associate professor of medicine at the University of Alberta, says it will probably take about ten years to get the answers-answers that can help reduce stomach-cancer rates not just in Aklavik, but in the rest of Canada, too. For now, though, Marshall would like to see testing for H. pylori be- come a standard part of medical checkups. “You could do it when you’re in your 40s, when you start checking your thyroid, your cholesterol,” he says. Quick treatment with antibiotics could be just as standard, he says. Plus, with early detection of and treatment for the H. pylori infection, he says, “you would never get stomach cancer.”
In 1996, Marshall received Canada’s Gairdner Award for his work. And in 2005, he was honoured with a Nobel Prize.
More Stealth Infections
In the early ’70s, a young American named Dr. R. Palmer Beasley was studying hepatitis B in Taiwan, where rates of the disease were high. Beasley was working at a research facility established by Seattle’s University of Washington. While learning how the disease was transmitted-from mother to newborn, among other ways-he came to realize that Taiwan also had an unusually high incidence of liver cancer. After more research, he postulated that hepatitis B caused the cancer.
“People thought I was crazy,” recalls Beasley, now a professor of epidemiology at the University of Texas, in
Houston. “I was told it was nonsense. The vision then was that the big answers would come from chemicals.” But Beasley persisted and, in 1975, began a landmark study that eventually showed liver cancer occurred almost exclusively in people who had been infected with hepatitis B-the majority of whom were carriers with no symptoms of liver disease.
Normally, liver cancer is fatal, killing almost 700,000 people every year. But now we can thwart it. Last year, a study showed that six-to-19-year-olds in Taiwan who received the hepatitis-B vaccine at birth had a 70-percent-lower risk of developing liver cancer than did those who weren’t vaccinated at birth. Cervical, stomach and liver cancers are the major ones triggered by infection. But less common ones-including those of the immune system (Burkitt’s lymphoma and Hodgkin’s disease), the larynx, the esophagus, the skin (Kaposi’s sarcoma and Merkel cell carcinoma)-arise the same way. “Globally, 21 percent of cancers are linked to infection,” says the German Cancer Research Centre’s Dr. zur Hausen. “This exceeds even the incidence of cancers linked to smoking, which is 18 percent globally. I suspect we’ll find more.”
The Work Goes On
Lorelei Mucci, an epidemiologist and assistant professor of medicine at the Harvard School of Public Health, recently completed a study of the link between sexual infection and prostate cancer. Results from the more-than-1,300 subjects showed that exposure to the common sexually transmitted infection trichomoniasis nearly triples a man’s risk of developing a particularly aggressive, lethal form of
Caused by a parasite-Trichomonas vaginalis-the infection “is silent in women,” Mucci explains. It rarely causes symptoms in males, either. “It lasts for a very long time,” she says.
“And it causes chronic inflammation, which damages cells and tissue, leading to precancerous changes.” If this association is confirmed by further research, some forms of prostate cancer could be prevented with a short course of antibiotics. “People used to believe trichomoniasis was not a serious disease,” Mucci says. “We now know we should be concerned about its long-term effects.” Worldwide, about 250,000 men die of prostate cancer every year; about four percent of American men develop an aggressive form of the disease.