To be a health reporter, in many ways, is to also be a cancer reporter. That's because much of what makes the medical news concerns cancer — how to avoid getting it, and how to survive it when it strikes. So, it's surprising to discover a potentially powerful tool against cancer that's not being used.

This week in The Lancet Oncology, a study reports that every year 2 million people in the world develop preventable cancers caused by infectious agents, bacteria and viruses, that could be detected and treated. That’s if someone went looking for them. It's called 'screening', the act of testing apparently healthy people for the seeds of future cancer.

"It is frustrating," Dr. Paul Moayyedi, told me. "I feel it's such a missed opportunity." He's a gastroenterologist from McMaster University in Hamilton, and he was talking about Helicobacter pylori, a type of bacteria that causes most gastric cancer, the second-leading cause of cancer death in the world. Half the world's population is walking around with this potentially deadly pathogen in their gut. Not everyone with H. pylori infection will develop cancer, but those unfortunate few will develop a ferocious disease that kills with brutal efficiency. Dr. Moayyedi said "if you are unlucky enough to get stomach cancer roughly your chances of surviving 5 years are one in five, 20 per cent, so most people sadly die and most within the first two years."

A transmission electron micrograph of a section of the surface of a human stomach infected with Helicobacter pylori bacteria in red. (Getty)

If the H. pylori infection is treated early enough, scientists believe those gastric cancer deaths could be prevented. So should Canadians be screened for it?

"I think they should," Dr. Moayyedi said. "That's the simple answer, although it's never as simple as that."

The screening test seems simple enough. A blood test will show if someone had been exposed, a follow-up breath test will tell if the bacteria is active, and then a short course of antibiotics will clear it up most of the time. Eliminating H. pylori would also reduce deaths from bleeding ulcers. So why don't we test everybody? It's the kind of naïve question a reporter gets to ask. Dr. Moayyedi said the idea has no traction in Canada.

"The benefits in cancer, in Canada, aren't as dramatic as they might be for something, like colon cancer,” he said, "and maybe politically it's not so exciting but still, every opportunity to save lives is a good one."

Ontario considered it back in 2004 when an expert committee agreed that "screening for and treatment of H. pylori may represent a significant opportunity for preventive oncology." In other words it could prevent cancer. Still, in the end, the committee decided not to recommend it. I had a chance to talk to University of Toronto health policy professor Terence Sullivan who was head of Cancer Care Ontario at the time and sat on that committee. He explained the thinking back then.

"At that stage we didn't feel that we had the justification to launch a mass screening program," he told me.

In other words, the number of lives saved wouldn't justify the cost. That's because, even though about 20 per cent of the Canadian population is infected, less than 2 per cent will get stomach cancer, resulting in fewer than 2,000 deaths a year in Canada.

Screening questions

Skeptics might suggest that a cancer with so few survivors means there are fewer people to lobby for testing. But there are other considerations too. Sometimes screening actually causes harm. There's the problem of over-treatment, finding and then invasively treating cancer that might not be fatal, an aspect of prostate and breast cancer screening that has been vigorously debated. In this case, experts speculate that treating more people for H. pylori infection could increase antibiotic resistance or create some other unanticipated health problem.

And it turns out that screening is complicated. You need protocols. A committee has to meet to write them. People need to be trained. Decisions need to be made. When do you do the test/scan/screening thing? What about follow up? Do you need a second test to make sure the first test/treatment really worked? Who pays for all of that? And where is the evidence that screening for the thing will actually save lives? For that, you need large randomized controlled trials. Who's going to pay for them? And how long do you wait? It takes time to follow a population to see who lives and who dies.

And that's why people are walking around right now, here in Canada, with cancer causing pathogens that could be treated, if they only knew they were infected. It’s not just H. pylori. Another cancer causing virus is hepatitis C. It quietly attacks the liver, leading to cirrhosis and cancer. A recent study showed hepatitis C kills more Americans than HIV and that's why one Canadian doctor thinks all baby boomers should be screened for the virus.

Hepatitis C in baby boomers

Dr. David Wong, the clinical director at Toronto Western Hospital's Liver Centre told me "if you're born between 1945 and 1965, a baby boomer, you actually have a reasonable chance of having hep C in North America. And all those people should routinely get hep C testing at least once."

"These infections cause close to zero symptoms," he said, "and you have these infections for 30, 40 years. And now someone might be 50 or 60 yrs old and they still may not know about it. You don't have symptoms until you have liver failure."

The treatment for hep C is expensive, with unpleasant side effects, but new drugs are raising the question of whether it’s time to start screening. A recent study in the Annals of Internal Medicine suggests it would be cost effective to screen baby boomers for hep C. As for H pylori, Dr. Moayyedi told me family doctors don't routinely check for it, even when someone complains of stomach pain.

"Probably about 5 to 10 per cent of family doctors will test for it routinely in someone with indigestion and I don't think anyone is testing for it just as a screening tool," he told me.

Preventable infections are causing 1.5 million cancer deaths worldwide, The Lancet Oncology study reports. That’s roughly one in five deaths due to cancer worldwide.

"Sadly most places where stomach cancer is common, they’re quite poor countries so they can’t afford to have screening programs," Dr. Moayyedi said. "But in Canada we can, so it would be good to do it." Will it ever happen? An official involved with cancer screening programs in Ontario said the question hasn’t come up lately, but that might change now that the issue of cancers caused by infections is making headlines.