Cancer expert Kelly Marcom, MD, discusses the role that genetics and environmental exposure play in the role of understanding why a person develops cancer. Dr. Marcom is a professor of medicine and member of the Duke Cancer Institute (DCI). He is part of a team of experts at DCI that offers genetic testing and counseling to people diagnosed with cancer, as well as people at risk of developing cancer. Transcript Lindsay Key: Welcome to HeadScratchers, a mini-cast from the Duke University School of Medicine. We ask Duke experts to help us understand the questions in science that have us scratching our heads. Today we're speaking with Dr. Kelly Marcom, an expert in genetics and cancer. Dr. Marcom, what are the factors that contribute to someone getting cancer? Dr. Kelly Marcom: Well, it's a very complex question, and one that we continue to work on very hard. Cancer is not a very intuitive disease process. Unlike a lot of things that affect our bodies, you know, you get a heart attack, you block a blood vessel -- those things are fairly straightforward. But cancer -- cancer is something that we don't naturally have a good intuitive understanding for. And it always then, consequently, is a bit of a mystery to many people why they got it. Fundamentally, cancer is a genetic disorder, by which I mean that the underlying cause of the problem is damage to the genes in the cells. But that understanding of cancer is really something that's still relatively recent. Watson and Crick identified DNA in the 50s, and so that began the whole process of understanding DNA and what it does. And, while people had always made observations about inherited patterns of cancer within families, it wasn't necessarily evident what the basis of that was. Now, prior to that time, there was a great deal of emphasis on the infectious nature of cancer, as caused by viruses. You can imagine, if you see cancer being transmitted through a family from one generation to the next, you might naturally assume that it's an infection. And there was a good scientific rationale for that: clearly it had been shown that certain viruses were responsible for certain types of cancer -- the most classic and probably one of the most important being cervical cancer, caused by papillomavirus. And so that whole story really came together with understanding that cancer is developed because you get damage to the DNA that perpetuates the additional damage to the DNA, and propagates itself through the cancer cells, and leads then to unregulated growth. And figuring out how those viruses cause cancer was in damaging DNA, and damaging things in the cells in the cervix in the course of the virus growing. So if genetics are the basis of the cancer, what is the influence of environmental exposures? Most of the things that contribute from a lifestyle have to do with exposing your body to things that damage your DNA. Smoking is the biggest culprit. Too much sun -- that's going to cause DNA damage. All those lifestyle factors, they all have some exposure that increases that risk for DNA damage. Ultimately, when we understand why cancers develop, it first helps us understand how to treat it, but then also we use it to help us understand how to screen people for cancer, and then ultimately -- hopefully -- a better understanding about how to prevent it. LK: Thanks for listening. This podcast was produced by the Duke University School of Medicine. Music by Blue Dot Sessions. Visit us online at headscratcherspodcast.duke.edu. You can also find us on all your favorite podcast players. Don't forget to hit the subscribe button! And if you like us, leave us a review