Cancer: What you can do to minimise your risk

David Whiteman:
G’day, Clare. How are you doing?

Clare Blake:
We often hear people talk about the cure for cancer, especially you, but cancer isn’t a single disease. It’s quite complex.

David Whiteman:
Cancer is really a process. So when in pathology, as students, we learn about the disease processes, we learn about infections and inflammation and cancer is like one of those. It’s a general description of a process in which the body’s cells have lost control and continue to grow. And cancers can occur in many different organs in the body. And so there are as many types of cancer as there are organs in the body, and then some.

Clare Blake:
What are the causes, like genetic, environmental, age? Can you narrow that down?

David Whiteman:
Yes, you can. You can start broadly, like at that high level to partition the causes into these broad categories. So we tend to think of things that exist outside of the body as environment and lifestyle. And then things that are inside the body can be genetic, they can be molecular. But we tend to break them down into smaller and smaller root causes until we find out for sure what causes particular kinds of cancer.

Clare Blake:
You’re an epidemiologist now, so what is the focus of your research?

David Whiteman:
Yeah, so epidemiology, I would like to think we’re the new rock stars in this post-COVID world. No one knew what an epidemiologist was before. They used to think we were some kind of skin doctor that looked at people’s skin, like a dermatologist or something. But epidemiologists really study disease in populations. We look at how common diseases are, in whom they occur, have there been changes over time. And then different branches of epidemiology look at the causes of disease, and so that’s what I do. I look at the causes and the sort of predisposing factors for cancers. My own work is predominantly in skin cancer and melanoma, but over my career I’ve looked at many different kinds of cancer and some of my work is still broad at that level.

Clare Blake:
How do epidemiologists establish or prove what factors might increase our risk of cancer or survival?

David Whiteman:
Yeah, it’s a sort of eternal question in epidemiology: When can you call something a cause? So about 60 or 70 years ago some pioneering epidemiologists developed a sort of core philosophy of epidemiology and there are criteria for establishing causality. So you have to have a risk factor that is consistently observed across different populations. It has to be a certain magnitude of effect, a strong risk factor. You’d like to see that there’s analogies from maybe the same risk factor acting in different parts of the body in similar ways to cause disease. So there’s a whole bunch of different criteria that we sort of checklist off before we have the courage to call it a cause. But your original question is how do you look at risk factors? Well, what we tend to do is do large studies gathering information on many people who have the cancer that you’re focused on, and then a representative group of other people who don’t have that cancer – controls, we call those people. Then we gather information from those two groups of people and compare them and things start to emerge that are different in the people who have cancer. And then you can start saying “Okay, those things that differ between those two groups of people, that’s interesting. We’ve got to find out more about that.” And that that becomes a risk factor.

Clare Blake: 
It’s huge amounts of data that you need to collect. I know that’s part of your job, finding those people to participate. Is that the hardest?

David Whiteman:
Oh, it’s one of the hardest. The hardest part is getting the money in the first place actually. So as researchers, we spend a lot of time writing grant applications, and that’s where you have to be able to put forward your hypothesis, put forward your research proposal and have other people criticize that to the nth degree. It’s got to be a better proposal than all the other ones that are out there at the same time. So getting the money is hard. Once you have the money, then yes, in epidemiology, recruiting people into studies is also hard. But we’ve had a good success here at the Institute. A lot of people know about our work and so when we send out letters, a lot of people say “Yes, I’ll take part,” but it takes a while to build that reputation and that’s something we treasure.

Clare Blake:
You also looked at how many cases of cancer and deaths from cancer and those different lifestyle or environmental factors are responsible for.

David Whiteman:
Yeah, that work uses… national datasets. So health departments around the world, and particularly in Australia, keep records of particular notifiable diseases, for things like rabies or particular kinds of infectious diseases. But they also keep very good records on occurrences of cancer. So every time a cancer diagnosis is made in Australia, that event is registered in a very secure database. But as researchers, if we meet certain criteria and can guarantee the privacy and safety of that data, then we can also access those registrations of cancer. So that’s a very powerful tool for looking at historical trends in cancer incidents. Does it affect men and women differently, different age groups differently? Has it changed over time? And that gives you really strong clues that things might be changing in the world of cancer. I’ve seen that in my career on a number of different cancers. So those things are very powerful tools, but it doesn’t require us to recruit patients. That data exists.

Clare Blake: 
And that’s all de-identified, so you never know who these people are.

David Whiteman: 
That’s right. And that data is very, very secure, but it’s quite rich. It carries a lot of information. So there’s a lot of important insights that can be gleaned from that kind of data set.

Clare Blake:
You’ve been able to put a number on just how many cancers in Australia could be prevented each year if everyone followed advice, as well as the number of cancer deaths that could be prevented. Those numbers are pretty extraordinary, aren’t they?

David Whiteman:
Yeah, they are. So this is work that we did with the Cancer Council. We started in about 2010 on this work. Their question was “If we could prevent cancer through things that we know about now, how many cases of cancer could we prevent in Australia each year?” That seemed like a simple question. There’s actually a lot behind that. So our group teamed up with others around the world. So first of all, what you have to come up with is a list of factors that everyone agrees do cause cancer. We had a list of about 13 factors that are changeable, that you can modify your exposure as a human – you can choose to smoke or not smoke, drink alcohol, not drink alcohol, eat a healthy diet, exercise more. These are the things you can change for which there is strong evidence that they are also causes of cancer. So the answer we came up with was in Australia each year out of the 140 000 cases of cancer each year, about 40 000 of them could be prevented through things that we already know about now. So that’s about one in three, a little bit under one in three cancers could be prevented.

Clare Blake:
That puts a lot of it back in our own hands. That’s an extraordinary number.

David Whiteman:
It is an extraordinary number. Now, knowing it is one thing, doing it is quite another. That is the challenge. And some of these things are not easily changeable. I mean, the requirements for physical activity means about 60 minutes of high-level activity a day. That’s almost unattainable for most people.

Clare Blake:
And a high level activity is different as you go through the different demographics. So, say, if you’re 70, you need to get your heart rate up to, say, 60 per cent.

David Whiteman:
Yeah, that’s right. There are different thresholds for what constitutes high-level activity. But the requirement of getting 60 minutes a day is the same for everybody. So that’s a lot of activity and beyond what most Western lifestyles can afford to dedicate to exercise. So that’s the absolute gold standard of what we could reduce our cancer burden by, but we should still aspire to do that. Even doing some is better than doing nothing.

Clare Blake:
Well, there’s so many things that can influence our risk, I suppose. I know you’re very careful to use the word cause. What are the best things that the average person can start doing to minimise their risk? Outside of the exercise, then there’s diet.

David Whiteman:
There’s diet. I mean, I would start at the very top of the list to say the best thing you can do is never start smoking. Ever. Smoking causes more cancers than any other thing in the world. It’s preventable. In fact, there’s no redeeming qualities to it. So my message to everyone is never smoke. If you do smoke, quit. Quit now.

Clare Blake:
Then let’s work down from there. I imagine alcohol is next.

David Whiteman:
Actually alcohol is not the next one. There’s a bit of a tight spot for second, third and fourth place. But actually, in Australia sunlight is a very important cause of cancer when you talk about melanomas and skin cancers. Now, they don’t kill a lot of people, but their toll on the health system is huge. You only have to walk the streets of Australian cities to see the amount of sun damage that’s out there. Each year in Australia we lose thousands of people to melanoma and skin cancer, and these are almost entirely preventable. So sunlight in Australia is actually one of our biggest causes of cancer. Then you’ve got things like diet, which is composed of different parts of the diet. So eating too much red meat, insufficient fruit, insufficient vegetables, and insufficient fibre. And in totality those four components of diet that cause cancer contribute about four or five per cent of the total cancer burden in Australia that’s preventable each year. So again, that’s thousands of people.

Clare Blake:
The World Health Organization declared processed meat was a carcinogen a while ago, and red meat was probably carcinogenic to humans. Can we eat any amount of processed meat safely?

David Whiteman:
Well, this was a very controversial ruling from the WHO and the jury goes backwards and forwards on whether this was a sensible proclamation to make. But the evidence is the evidence and the data are the data. So people who eat red meat have higher risks of bowel cancer than people who don’t eat red meat, than vegetarians, and that’s an inescapable fact. But red meat has many benefits as well – Vitamin B12, and protein, and iron, and things like this – so it’s actually an important part of your diet. A lot of the effect of meat comes from the way it’s cooked. So when people cook it at high temperatures or they fry it or they broil it as they do in America or barbecue it…

Clare Blake:
So all the good bits, you’re saying?

David Whiteman:
Yeah, all the tasty bits. That process of cooking at high temperatures leads to charcoal-type compounds on the outside that are actually quite potent carcinogens. So a lot of the effect we think is from the way it’s cooked. And so people can substitute with white meats, fish, chicken, things like that and…

Clare Blake:
Do it in a slow cooker.

David Whiteman:
Or do it in a slow cooker.

Clare Blake:
Do people need to go, how far? Do we need to live on kale and mung beans? Or is there a balance, like you said before, fruit and vegetables?

David Whiteman:
Yeah, look and I’m not here to give lifestyle advice. I particularly look at the data. I don’t give cooking advice either, I’ve got to tell you. In my own personal life, I eat meat and I still like to eat meat. I think it’s an important part of my diet, but I am mindful that I don’t need all that much of it to be healthy. I also know that if I eat meat that’s been cooked in these various ways that there is a risk. I mean, there is an inescapable risk that that will cause damage to my colon, and therefore there’s a risk of cancer in the future. So it’s like a lot of things in life, you have to be able to weigh the risks and benefits.

Clare Blake:
And of course, if we’re too prescriptive in the advice and it seems too hard to follow, then some people won’t try at all. Something is better than nothing?

David Whiteman:
Yeah, and look, it’s fair to say though, even in Australia and New Zealand and the US, the quantities of meat that people eat, the red meat, is actually decreasing over time as a sort of natural change in the way people eat these days. And in fact, you’d be surprised maybe to think that our alcohol consumption has also decreased quite markedly per unit of population. So there are still some people who drink a lot, but in the main, people drink less now than they did a generation ago. So these are sort of cultural changes that sweep through society as well. So in some ways the work gets easier as we learn more and everyone changes.

Clare Blake: 
Does your evidence show that there is a safe level of alcohol, or is none the best?

David Whiteman:
Again, this is where the data come in. People have looked at this question really in a lot of detail as well, but when you draw the regression plots – that is, comparing alcohol intake with risks of cancer – there really doesn’t seem to be a threshold for cancers. Even at low intakes of [alcohol], people have a slightly higher risk than people who don’t drink at all. So the advice at the moment is there is no totally safe lower limit of alcohol, but really when you look at the data, most of the bad effects are coming at higher levels of drinking, quite markedly higher levels of drinking. So many doctors would still choose to drink a little bit, in moderation.

Clare Blake:
Is cancer becoming more common, or is it better diagnosed?

David Whiteman:
Well, a bit of both, but it is becoming more common and a large part of that is driven by our ageing population. So cancer becomes more common as we age because more things can go wrong in your cells, they get more mutations and bad things happen. So as we age, cancer becomes more common. We also survive more, if you know what I mean. So people have lived through those diseases of early childhood that used to take people out. So there’s more of us surviving into ages at which we get cancer, as well as age being a risk factor on its own. Then yes, we are diagnosing more. So because of things like screening programs, prostate screening, bowel cancer screening, breast cancer screening, and we have more people who live with cancer than die from cancer, so that’s all part of the equation.

Clare Blake:
You mentioned melanoma and skin cancer before. You’re one of Australia’s leading skin cancer and melanoma researchers. Do we know what proportion of melanomas is caused by that sunlight?

David Whiteman:
Yeah. For melanomas, the estimates are somewhere between 80 and 90 per cent are caused by sunlight. Some people might say it’s even higher than that, but I think our data suggests it’s about 80 to 90 per cent. So that means a proportion of them are going to happen anyway, are sort of genetically programmed to occur. And we know that from a range of different scenarios, but even when you go right back into Victorian England, when people were sort of working 12 hour days, six [days a week], down the coal mines covered from head to toe, wearing hats all of the time, there was still a melanoma rate that occurred in the population and people would die from melanoma even in England, even in the 1800s. And that’s when data were pretty reliable and the diagnosis was reliable. So there’s always been a baseline rate of melanoma, but we’ve seen an explosion since white skinned people arrived in Australia and lived in this tropical environment and didn’t cover up.

Clare Blake:
What are the other most common cancers?

David Whiteman:
In Australia? In the Western world? So in men, prostate cancer is the most common, followed by bowel cancer and then lung cancer. In women, it’s breast cancer, bowel cancer, lung cancer, and then melanoma comes in at number four or number three. It changes a little bit each year. Those cancers occur at about the same rate.

Clare Blake:
And some are more deadly.

David Whiteman:
They are. So different cancers in different organs of the body go bad at different rates. It tends to be that cancers that are in organs that are deeply buried in the body – so things like pancreatic cancer, ovarian cancer, brain cancer – do badly. A part of that is that they are hard to diagnose until they’re quite large and quite advanced and so people don’t even know that they’ve got them until the tumor has spread, and that’s very hard to treat. But some cancers are just very aggressive from the get-go. They’re difficult for clinicians to know what to do with.

Clare Blake:
And some respond better to treatment, and I know that you’ve also studied a lot of esophageal cancer. Is that on the rise?

David Whiteman:
It has been, yeah. So there’s two main different types of cancer of the oesophagus. It’s one of those organs that different populations of cells can get the cancer. In the past, the common kind that used to occur in Australia was caused by smoking and alcohol. It was typically a disease seen in sort of down-and-outs in a way – people who did a lot of damage to their body through smoking and alcohol. But there’s another kind called adenocarcinoma of the oesophagus. It’s become much more common in Australia and America and Northern Europe in about the last 30 years. And it seems that that’s related to reflux, acid reflux coming up from the stomach into the oesophagus, but also obesity. And it’s much more common in men than women, about eight times more common in men than women.

Clare Blake:
That type of oesophageal cancer, or both?

David Whiteman:
No, just that kind, that one kind. What appears to be driving it, we’ve done a lot of research in this area and others have too, but it appears to be that the way in which men become obese is they get the beer belly. They get deposits of fat in the abdomen and that kind of fat location leads to the fat releasing all kinds of inflammatory mediators that seems to have a potent effect on the oesophagus. So that appears to be what’s driving it.

Clare Blake: 
Similar to heart disease, where if the fat is hard and close to the organs, it’s a bit more dangerous?

David Whiteman:
Yeah, it doesn’t seem to be a physical proximity thing. It’s more that the fat that occurs in the abdomen, which men tend to put down, that sort of beer belly type of fat, is more metabolically active. Women tend to put fat down underneath their skin, so it’s called subcutaneous fat, getting into the details.

Clare Blake:
We start out with a lot more of that anyway, don’t we?

David Whiteman:
Yeah. So men and women have different body shapes and different depositions of fat around the body and women’s fat, or subcutaneous fat, even in men, tends to release oestrogens and hormones, whereas male pattern fat is more metabolic. So it releases things that tend to be bad for us.

Clare Blake:
How far have we come in cancer treatment? It seems like we’re really on the edge of new knowledge.

David Whiteman:
Oh, have we definitely are. I mean, even in my career, when I first started going to melanoma conferences back in the 1990s, the treatments for melanoma that were advanced were just non-existent, they were terrible. And the conferences would always close on a slightly dismal note because while progress was made in treating the primary cancer with an excision or surgical approach that was pretty good, if the melanomas had spread to other parts of the body, then the chemotherapy just didn’t work and radiotherapy didn’t work. Then about 10 years ago, these new treatments, these immune modulating treatments, started to first appear and showed a bit of promise. And in the period of time since then, they’ve just revolutionised melanoma treatment and they’re starting to be used in other cancers as well.

Clare Blake:
Some lung cancers, is that right?

David Whiteman:
Yeah. Certain types of lung cancer, certain types of kidney cancer, head and neck cancer. So they’re being used for numbers of different cancers and now that we have some of the secrets of how those therapies work, they can be targeted and sort of reprogrammed to work for a lot of different cancers. So there’s a lot of hope that we can trick the body’s immune system into fighting these cancers for us.

Clare Blake:
And enjoy those conferences a little bit more.

David Whiteman:
Hopefully, yeah. Hopefully they’re more positive. Yes.

Clare Blake:
David, is there one thing about cancer prevention and survival that you just wish everybody knew?

David Whiteman:
Well, that’s a very good question. I really strongly believe that we should make sure people never smoke. It’s a terrible habit. It has terrible consequences. But going beyond that, I think leading a active, healthy lifestyle and eating well, eating diversely, they’re really quite low-tech solutions that people can adopt in their own life to [minimise] their risk of cancer, and they go a long way. Keeping their weight under control, but if you’re being active and eating well, you won’t have to worry about your weight. So that package of lifestyle [factors] can actually have a big effect.

Clare Blake:
And where do you sit on sunscreen?

David Whiteman:
Oh, yes. Yeah. Sunscreen is something you really have to use every day in Australia, particularly in northern Australia and Queensland, and particularly in the summer months. Slip, slop, slap, so important. And start young. Start young.

Clare Blake:
This information is general in nature. For personal advice, your own health professional is definitely the best choice. Thank you very much, David. It’s been fascinating, and for more on Professor David Whiteman’s extraordinary contributions and current work and any of our research, qimrberghofer.edu.au. Thanks David.

David Whiteman:
Thank you.