Transcription:
Cancer Causes and Risk Factors

Melanie Cole (Host):  Researchers in the Department of Population Sciences at City of Hope are working to better understand the causes of cancer, including hereditary, genetic and environmental factors that may influence a person's risk of developing cancer. My guest today is Dr. James Lacey. He's an Associate Professor at City of Hope's Division of Cancer Etiology and a member of the Cancer Control and Population Sciences Program. Welcome to the show, Dr. Lacey. Tell us a little bit about what actually –we hear about a million different types of cancer—what is cancer?

Dr. James Lacey (Guest):  What is cancer? It's a good question. Cancer is abnormal growth of the normal cells in our body. What is supposed to happen as we go through life is our cells, organs, or systems are naturally growing and dying and there's an order process to that. If the cells continue to grow uncontrolled, then that becomes cancer, and that uncontrolled growth is what causes the problems we associate with cancer.

Melanie:  We hear about many different causes, risk factors, things out there that can cause cancer. Tell us what you, studying etiology for a living and an expert, find as some of the most main causes and most main risk factors for cancer.

Dr. Lacey:  When we refer to cancer, we're really talking about a collection of different cancers. Each cancer that occurs in a different tissue of the body, for example, breast cancer versus lung cancer is slightly different. Nonetheless, there are two common risk factors that tend to affect a lot of cancers. One that most people have heard about is smoking. Even though fewer people are smoking today, smoking is still a major cause of lung cancer and other cancers. Two other ones that people hear about for a good reason are exercise and obesity. We're learning more and more about how obesity can increase the risk of a whole range of cancers. And exercise as well, both because of its ability to maintain a healthy body weight and because of some of the mechanisms of the body, exercise seems to reduce some risks of cancer.

Melanie:  What role does genetics play? People always want to know family history, and if somebody in your family has lung cancer, or lymphoma, or breast cancer, does that mean that you are at higher risk for most of these cancers? Do most of them follow a genetic line?

Dr. Lacey:  We've known for years that almost every cancer is a combination of genetics and environment. And what's been really exciting in research for the last 20, 30 years is we've got much better tools now to measure the genetic component of it. Family history is one thing that captures some of that genetic risk. If a woman has a mother who had breast cancer and an aunt who had ovarian cancer, those combinations of the same types of cancers within a family in two or three generations tell us as researchers that there are some strong genetic influences on those cancers. Now on the whole, genetics are really I would say the primary cause for a subset of all cancers. For the majority of cancers that occur among older adults, it's really a combination of genes and environment, and that's where some of the work we're doing is trying to tease out the specific effect of, say, genetics plus smoking, or genetics plus obesity, to determine what's going on there.

Melanie:  We hear so much about diet, nutrition.  These foods are carcinogenic, these foods cause cancer, these foods don't; these foods cause, you know, fight cancer, help fight cancer. Tell us a little bit about diet, nutrition. Where are we going in the field of diet and nutrition toward cancer?

Dr. Lacey:  It's been a fascinating part of our research to watch. At the broad level, if you compare populations with certain kinds of diet to populations that tend to eat different kinds of diet, you can see some distinct and real differences in the risk of cancer. So, it appears that some of those differences are real and they can turn into significant differences in cancer risk. We also know that the purpose of diet is to give our body and ourselves the energy that it need to keep living and dividing and growing. At a simplistic level, the better food we eat, the better energy those cells have. And there's a third level as well. Particular nutrients; micronutrients, macronutrients, vitamins can have specific effects on some of those mechanisms in the body, how well can our cells pick up, repair and fix little changes that might turn into cancer. So, what we see in diet is there's an attempt both to understand what does a specific vitamin or mineral or type of food do, and also at the broader level, what do patterns or types of activities mean for a person with cancer risk?

Melanie:  So then when we're looking at all of those and we're thinking about carcinogens that are just part of our environment, so obviously other places you see less cancer based on their environment or what they eat or how much activity that they get in a day, but if you live in a city and you're taking the bus and you're standing by the train, are you exposing your body to more of these carcinogens, Dr. Lacey, and thereby increasing your risk?

Dr. Lacey:  Yes and no, and that's where we get into the issue of how do we balance these risks to understand the risk and the benefit? We're exposed to those types of risks every day in our normal activities. Not everything we eat at breakfast is good for us, not everything we eat at breakfast is bad for us. The body is very good at both utilizing the energy we give it and also controlling those risks that you talked about. So even if we breathe in a little bit of exhaust from a bus that passes us on our walk to work in the morning, the lungs and the immune system have a very good way of taking those pollutants, so to speak, and wrapping them up in the immune system and kicking them out so that they don't affect our body. Think of the body as having a very good defense mechanism. What we see though is that sometimes either the volume of the risks that impact our body—and the tobacco smoking is a good example of this—if someone is smoking cigarette for 10 years, it overwhelms the body's ability to manage and control and get rid of those pollutants. So that's one of the ways that can increase the person's risk of cancer.

Melanie:  So then if we're exposed to all of these things and our body's immune system is able to generally fight it off—I mean that must be true because the whole entire population doesn’t have cancer—what about things like radiation, naturally occurring radiation, or the radiation that we're getting from a mammogram or some of these annual exams and the X-ray? Do any of those contribute?

Dr. Lacey:  When you say "contribute", we can answer at a theoretical level and say yes. But I think it's much more useful to then take that theoretical "yes" and turn it into specific information that people can use. What we're seeing in the radiation field, and take mammogram for breast cancer for example, is an ability to quantify those risks and then we can tell the public, we can tell individual patients, “This is a very small risk and we think the benefits outweigh the risks,” or we can say, “This is maybe a risk that should lead to some differences in behavior.” For mammogram, the benefits of early detection of cancer, and that's really what a mammogram is supposed to do, find those breast cancers before we would be able to diagnose them in a clinical setting, so early detection leads to better outcomes. It reduces a person's risk of dying of cancer and it tends to detect the cancer at a stage when it's still treatable. For mammograms, there is a small amount of radiation involved with those mammograms, and a wealth of research has shown that if mammograms are given to the right population at the right frequency that increases the ability to achieve early detection, then the overall radiation that that group is exposed to is small and it's an acceptable risk because the benefits outweigh that risk.

Melanie:  Dr. Lacey in just the last few minutes if you would, give the listeners your best advice for where you think the horizon of cancer control, prevention, diagnosis, where that's going and why they should come to City of Hope for cancer care.

Dr. Lacey:  Control, prevention and diagnosis, if we could control all of those things we'd be in good shape, but we're making real progress on each of those. Prevention still comes down to a lot of individual decisions and the things we've all heard of: don’t smoke, eat a healthy diet, exercise regularly, get cancer screening, don't be out in the sun too much without sunscreen, and know your family history. The goal of all that information is to help people prevent cancers that might otherwise occur. If we're consistently engaging in those healthy behaviors, consistently getting recommended screening exams, are good ways to prevent cancer from appearing too late. On the diagnostic front, a lot of the work at the City of Hope is targeted at trying to detect those cancers earlier. And then once we know what those cancers are, find their specific types. What at the cellular level is driving those cancers? That's where a lot of the focus then is taking that knowledge about the nuts and bolts of cancer and then using that to develop targeted therapies. We're seeing that work in a number of cancers and that's a whole lot of excitement on the field right now that this approach can be expanded to a number of other cancers and improve cancer control of the population. 

Melanie:  Thank you so much. It’s great information. You're listening to City of Hope Radio. For more information, you can go to cityofhope.org, that's cityofhope.org. This is Melanie Cole, thanks so much for listening.