In 2015, we heard that processed meat was carcinogenic to humans, and red meat probably was too. In 2016, it was “very hot” drinks, but not coffee specifically (thank goodness). And with Monsanto back in the news in 2018, we were reminded that glyphosate the active ingredient in common weed-killers was “probably carcinogenic” too. But what does that really mean and why are there so many mixed messages about what causes cancer?
Cancer science misreported and misinterpreted
In each of the examples above, the alert was sounded by the International Agency for Research on Cancer (IARC) at the World Health Organisation (WHO), as part of its Monographs Program. A big part of the IARC’s role is to bring together scientific experts to identify things that cause cancer, based on the available scientific evidence. Every year, cancer biologist Darren Saunders from the University of New South Wales braces himself for the release of the IARC reports. “You can almost mark it in your diary every year when they release a report, and know that it’s going to be misconstrued and misinterpreted by everybody,” Dr Saunders said. The problem, he said, was how the reports were communicated to the media and the public. “They put these statements out there, and then they leave all of the work up to people like me to try and interpret this information for people.”
The difference between hazard and risk
When the IARC releases a report, the potentially carcinogenic agents examined are placed into one of the following groups:
- Group 1 Carcinogenic to humans, eg. solar radiation (sunlight), smoking, eating processed meat
- Group 2A Probably carcinogenic to humans, eg. eating red meat, glyphosate
- Group 2B Possibly carcinogenic to humans, eg. coffee
- Group 3 Carcinogenicity not classifiable, eg. tea
- Group 4 Probably not carcinogenic to humans, eg. caprolactam a chemical used to make synthetic fibres
But these groupings only describe the amount of evidence there is that a substance is carcinogenic not how carcinogenic it is. So, you can end up with two different carcinogens in the same IARC grouping, where one will hugely increase your risk of getting cancer and the other might just shift it by a minuscule percentage, Dr Saunders said. For example, processed meat including salami, sausages and bacon is in Group 1, along with tobacco smoke, plutonium, asbestos and even sunlight (solar radiation). “If you eat processed meat, yes, it might slightly increase your chances of getting cancer,” Dr Saunders said. “But if you get exposed to tobacco smoke or plutonium, you have a really big chance of getting cancer. “So even though the evidence puts smoking and processed meat in the same [IARC] group, the relative risk of those carcinogens causing cancer is not equivalent.” He said this was a point that was often missed by media covering IARC cancer findings, even though the agency did provide that information. The IARC said it monitored how the media and public responded to its reports and adjusted its communications accordingly. “There has been a real effort to develop, adapt and improve the communication materials we produced to better reach a lay audience,” the agency said in a statement. “Not all products of this agency are palatable to the broader public, but when they do have clear public health significance, we produce a ‘comms’ strategy and roll it out.”
Salami and cigarettes
Weighing up the cancer risk of smoking versus eating processed meat is something that the Cancer Council has to consider when planning its education campaigns. Unlike occasionally eating sausages or ham, there is no safe level of smoking and this is critical for the way that risk is communicated, according to Anita Dessaix, director of cancer prevention and advocacy at Cancer Council New South Wales. “The relative risk of consuming too much processed meat is a lot smaller compared to something like tobacco,” Ms Dessaix said. So, the Cancer Council focuses its efforts on what will make the most difference to the community. “We assess the evidence, look at the relative risk of different products or carcinogens, and ensure that we’re communicating to the public in a way that can make the biggest gains to improve their lifestyle and, in effect, reduce their cancer risk,” she said.
Making sense of contradictory health headlines
It seems every day there’s a new piece of health advice that contradicts yesterday’s advice. Here’s how to sort science from pseudoscience. “When agencies like IARC release this type of content, we have to make sure we’re framing it in a way that’s not just raising fear for fear’s sake, but actually providing practical information.” Dr Saunders said when the IARC findings about meat came out, he spoke to a chef concerned about the effect on his business. “I was discussing this problem with a chef and he said, ‘All my customers aren’t going to want to eat steak anymore’,” Dr Saunders said. “I told him that if you put it into context, driving a car to the restaurant, drinking a couple of glasses of red wine, and then smoking a cigarette on the way home are all far more likely to increase your risk of cancer than having a steak. “He looked at me and said, ‘I hadn’t thought of it like that before’.” When people see cancer in the media, scientific evidence does not really factor into their response, according to science communication expert Rod Lamberts from the Australian National University. “The reality of the human calculation is that risk equals ‘what the f**k’ times ‘oh my god’,” Dr Lamberts said. “Which is basically how horrifying does it sound, and how bad would it be if it happened to you. “So, it’s not about the reality of it scientifically it’s just about whether it sounds horrific or not.” A common garden chemical that could give us cancer is bound to get our hackles up, Dr Lamberts said. “Cancer is horrifying, and the idea you get it from your gardening would outrage you, therefore people are freaked out,” he said. The 2015 IARC report on glyphosate concluded that “glyphosate is probably carcinogenic to humans” and placed it in the category Group 2A along with consuming red meat, drinking very hot beverages, and shift work that disrupts your circadian rhythm. Glyphosate resurfaced in the news this year when a jury in a US court case declared the weed-killing product Roundup was a factor in causing a man’s terminal cancer, and that the company Monsanto (now Bauer) failed to warn of its risks. Despite the IARC using considered language, stating that there was “limited evidence in humans for the carcinogenicity of glyphosate” and that “a positive association has been observed for non-Hodgkin lymphoma”, the looming shadow of a chemical giant can influence how people think about glyphosate and cancer. Dr Lamberts said when it came to dealing with big corporations like Monsanto, “hardcore tribalism” often kicked in. “Monsanto is cast as the nasty company that doesn’t give a toss about anyone else. Which means that any negative stuff [about glyphosate and cancer] is going to be believed and amplified,” he said.
Beware sensational cancer headlines
Despite researchers’ best efforts, the news media’s need for attention-grabbing headlines often trumps careful consideration of the evidence. “Sensationalism sells,” an IARC spokesperson said, referring to media coverage following the processed meat findings in 2015. “We did see a few media outlets particularly in the English-language coverage that played on fears and confused the public, without asking their source any questions. “This was compounded by the huge vested interests that felt that these results were an obstacle to their activities, and had a clear interest in denigrating the process, the results and their communication.” The ABC published six articles within three days following the IARC report detailing and clarifying what the findings really meant for people, and recognising the distress felt by industry from alarming-sounding headlines. Misleading health headlines are nothing new. But when it comes to stories about cancer, the consequences of poor reporting can be real, and serious. Dr Saunders said misreporting of cancer science including IARC findings can confuse cancer patients about their disease and recovery. Once people have a cancer diagnosis, the stakes are high. “A lot of people misunderstand that just because something might be a risk factor for giving you cancer, like smoking, doesn’t mean that if you take away that thing away it will act as a therapy or cure,” he said. “There are particular things in the diet that make us more susceptible to getting cancer, but taking those things out of your diet once you’ve got cancer isn’t necessarily going to make the cancer go away.” Another risk of unclear media coverage of cancer is that it can play into a public perception that nearly everything causes cancer, Ms Dessaix said. “There’s this situation where you can feel the community throw their arms up in the air and say, ‘There’s nothing that we can do, everything causes cancer, we give up’.” And that is why they are careful to communicate with the public effectively about their cancer risk, she said. Ms Dessaix encouraged people to contact agencies like the Cancer Council or their doctor if they were worried about something they had seen in the news about cancer. “If they do want further information about cancer risk factors, or if they’re going through a cancer experience, anyone can reach out to our support line (13 11 20),” she said.
ABC News, 24 November 2018 ; http://www.abc.net.au/news/