SECOND OPINION | Scary cancer statistic is not personal

Hello and happy Saturday! Here’s our roundup of the week’s interesting and eclectic news in health and medical science.

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There’s a way to cut cancer rates by 50%.  Why wasn’t that the Canadian Cancer Society headline?

It’s a question we asked this week with the release of the 2017 Canadian cancer statistics report. It’s an annual event the media treats as “news” even though cancer statistics change very little from one year to the next. That means much depends on the headline.

Every year the Canadian Cancer Society chooses what they want the story to be. Then they highlight their chosen angle in the accompanying news release. They send the media materials to reporters days in advance and insist that nothing be published until they say it’s OK. This year, they set their embargo for Tuesday, June 20, at exactly 3:01 a.m. ET.

So on Tuesday Canadians woke up to the alarming news that nearly one in two of them will get cancer.

It’s a headline that has the potential to be gravely misleading if anyone assumes they personally have a 50/50 chance of getting cancer. There was a reassuring caveat, buried deep in the report, that “the estimated probabilities are for the general Canadian population and should not be interpreted as an individual’s risk.”

The other problem with the headline is that it’s not new. For years, cancer epidemiologists have estimated the lifetime probability of cancer at around 50 per cent.

The only difference this year was the way the statisticians crunched their numbers. It’s a tweak that changed the incidence rate by a fraction of a percentage point over last year. 

The scary headline also misses the good news in this report. 

‘Because we are healthier, we grow old enough to get cancer.’- Dr. James Dickinson, University of Calgary

It is not as bad as first appears,” said Dr. James Dickinson, professor of family medicine at the University of Calgary. “This is likely the healthiest generation in history. The number of smokers is dropping, so smoking-related cancers [lung, larynx, bladder] are dropping. Other environmental pollutants and work-related carcinogens [like asbestos, arsenic and hydrocarbons] are less, or are protected against.”

We’re also surviving other diseases that used to be deadly, he told CBC Health. So people are living longer, which also means they have more time to develop cancer.

So it is a paradox: because we are healthier, we grow old enough to get cancer.”

And there’s the new problem of overdiagnosis, as high-tech screening detects cancers that may not be destined to be deadly. That results in overtreatment with powerful drugs and other interventions that have their own risks.

“Modern diagnostic testing finds more tiny growths that look like cancer but do not grow like cancer and would not kill, as we tend to think cancer does,” said Dickinson. “These include most prostate cancers, most thyroid cancers, most melanomas, many breast cancers, many kidney cancers, many colon cancers.

“Working out the difference, so we do not scare people without cause is difficult work for the future.”

We asked Dr Leigh Smith, the Canadian Cancer Society’s epidemiologist, if the decision to highlight this statistic was a deliberate attempt to make the cancer risk seem worse.

“No, absolutely not. We’re trying to give a realistic picture of what is going on with cancer in Canada,” she said. “I think this is really a reminder of the important challenges we face with cancer in Canada, especially as our population ages and grows.”

She said there is a lot people can do to reduce the risk of getting cancer, like quitting smoking, exercising, eating well, protecting ourselves against the sun and reducing alcohol consumption.

“We know now that about 50 per cent of cancers are preventable,” she said.

Now that sounds like a headline.

The science of forgetting

What if forgetting is not a failure of memory? What if it’s a feature of a healthy brain? Those are the head-scratching questions that a team of Toronto scientists is investigating.

It started with a surprising discovery by Paul Frankland, of Toronto’s Sick Kids Hospital. His group found a mechanism in the mouse brain that promoted memory loss. But it didn’t make sense — why would the brain expend energy trying to get rid of memory? The failure to recall something is typically seen as a flaw in the neural systems.

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It’s possible our brains are designed to forget some things, to not be a scrapbook of our lives. That’s why we invented photographs, video cameras and USB keys. (matkub2499/Shutterstock)

Collaborator Blake Richards, at the University of Toronto, is an expert in artificial intelligence, and he knew that AI systems are designed to deliberately forget because too much detail can interfere with their ability to perceive general patterns, and that can inhibit learning.

“What if the human brain does the same thing?” he asked. So Richards and Frankland began scouring the literature to see if other scientists had found evidence of neural mechanisms that induce forgetting. They compiled their findings in a review paper published this week in the journal Neuron.

“So if we’re right, then a healthy brain is one that does forget things,” he told us.

“The brain evolved to help you make decisions, and sometimes the best way to to make decisions is to forget some of the things that have happened to you and some of the things you’ve seen.”

Our brains are not supposed to be a scrapbook of our lives. That’s why we invented photographs, video cameras and USB keys.

West Nile virus goes west

According to a report out of the L.A. Times, a San Gabriel Valley resident is the first citizen of Los Angeles County to be hospitalized with a case of West Nile virus this year.

It’s a reminder that the virus has completed its mosquito-borne journey across the North American continent, a trip that began fewer than 20 years ago.

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Los Angeles County’s first West Nile virus case of the year was detected in March — a reminder that the virus has completed its mosquito-borne journey across the North American continent. The patient has since recovered. (Justin Sullivan/Getty Images)

The first human known to be infected with the potentially deadly pathogen was from the West Nile district of Uganda. That was back in 1937. By the 1960s, the virus was causing outbreaks in Europe.

But there were no human cases in North America until the summer of 1999. That’s when an unusual cluster of encephalitis in the New York City borough of Queens sent public health officials searching for a new bug. By the end of that summer, 59 people in New York City had been hospitalized with West Nile infections, sounding the alarm for the rest of the continent.

Ontario had more than 400 human cases in 2002. By 2012, there had only been a few cases reported in Alberta and Saskatchewan. But now the B.C. Centre for Disease Control calls it “the most widely distributed vector-borne disease in North America.”

The virus can be fatal, and there’s still no vaccine. But the University of Manitoba’s Dr. Michael Drebot was quick to point out that approximately 80 per cent of individuals infected with West Nile display no symptoms at all — other than an itchy mosquito bite.

We recommend…

Here are some other stories we found interesting this week:

Psst, the human genome was never completely sequenced. Some scientists say it should be l Stat

What is the most underappreciated medical invention in history? The Atlantic

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