Episode Transcript
Dr. Jones: Cancer in humans is a result of bad luck, bad genes or bad behavior, or a combination of the three. You can't change your luck or your genes, but let's talk about behavior. This is Dr. Kirtly Jones from Obstetrics and Gynecology at the 麻豆学生精品版 Care and this is "Cancer and Bad Behavior" on The Scope.
Announcer: Covering all aspects of women's health, this is "The Seven Domains of Women's Health" with Dr. Kirtly Jones on The Scope.
Dr. Jones: It's been said that the risk of getting cancer is about one-third chance, one-third your genetic predisposition, and one-third your behavior. Now, you can argue about those rough fractions and some would add another one-third environmental factors, but oops, that's four-thirds. But anyway, cancers are us.
There is a gene that helps prevent cancer called p-53. Elephants rarely get cancers. Now, they don't smoke and they don't get sexually transmitted diseases that we know about. Anyway, they have 20 pairs of p-53 and we all have one pair. People who inherit a faulty copy of that one and only p-53 gene have a 90% chance of getting cancer in their lifetime.
Those of us who have our normal one pair have about 25% chance of dying from cancer in our lifetime. So cancers are us. It's how we evolved and one of the many reasons we are different from elephants. But does that mean there's nothing you can do about getting cancer? I said cancer was one-third bad luck, one-third genes and one-third bad behavior, and let's throw in the environmental risk into that group.
Of course, most cancers are a combination of several of these factors, but what cancers are more likely to be influenced by behavior and what can we do? The poster child for bad behavior causing cancer is lung cancer and cigarette smoking, or exposure to secondhand smoke.
In developing countries where women don't smoke cigarettes, they do smoke the irritating small hydrocarbon molecules involved in cooking over wood fires in an enclosed area, small house or a hut. Some of this is bad behavior that can be changed. Cigarette smoking, either directly or with secondhand smoke, can be changed and we are changing by helping different cooking tools for women in poor countries. We can do something about this.
Of course, some lung cancers are generic and some are bad luck. There's an increased risk of lung cancer with radon exposure, but you can check the radon in your house and the basement easily by calling your health department. And if your radon levels are elevated, you can put a little fan in your basement, an easy behavioral change.
While we're on smoking, we can talk about oral cancers and esophageal cancer, which are increased in smokers and smokeless tobacco products. We might as well throw an alcohol, which is a risk factor for oral cancers as well. Of course, we all know the people who smoked or chewed all their lives and didn't get cancer, and that's where luck comes in or maybe these people had some elephant genes.
Now, cervical, rectal and oral cancers are related to sex and smoking. The two together are particularly risky. The sex part is that these cancers are related to the HPV virus, which is transmitted sexually. So if you never smoke and you never had any kind of sex, you won't get these cancers.
"Wait," you say, "No sex ever?" Well, it's hard to know if your partner or partners have HPV and it's hard to choose a life with no sexual contact ever, although some people do. But you can be careful. Limit your numbers of sexual partners. Practice safer sex with condoms and have your parents get you the HPV vaccine when you're 13 to lower your risk.
Liver cancers and hepatitis B and C. The most common kind of liver cancer, hepatocellular carcinoma, has about 80% association with hepatitis B and C. You can get hepatitis B and C from blood and sexual exposure. We screen our blood supply for these viruses, but people who do injected drugs and share needles are at risk.
You can also get these viruses passed down from your mom. Hepatitis B is more likely to be passed on to your baby than C, but there are good vaccines for hepatitis B and babies of moms with hepatitis B can get special treatment at birth to decrease their risk. Again, you have to be careful with your needles and your sex.
Now, skin cancers are related to sun exposure. Sixty-five percent to 85% of melanomas, the most deadly kind of skin cancer, are related to sun exposure. Ninety percent of non-melanoma basal cell and squamous cell cancers are related to sun exposure. Well, we evolved in the sun and sunshine is good for us in many ways, but there's too much of a good thing. So sun block from the time you're a kid will very substantially decrease the risk of common skin cancers as well as melanoma.
And you won't get wrinkled. Just think about how smooth the skin is on your tummy and how wrinkled it is on your hands and the face.Well, those of us over 60, we never had our tummies hanging out in the sun. And remember that you almost never get skin cancers on your tummy.
These are just a few and those are the easiest targets for behavior of change. A paper in the scientific journal Nature from January 2016 looked at the risks of cancer contributed by external factors, not genes or bad luck. The title was "Substantial Contribution of External Risk-Factors to Cancer Development." I would suggest that all the Scope listeners look it up and read it, but the math was much too hard for me and it made me a little dizzy.
So you can get the gist of it by scanning it or from this little podcast. The biggest risk for starting those bad behaviors that can lead to cancers are in young people, those who start smoking, have sex without protection and lay out in the sun. And you can tell your kids about these risks and they probably won't listen to you. But you can make sunscreen a habit for your kids from infancy. You can model good behavior by not smoking inside or outside your house, and you can get your kids vaccinated against HPV and hepatitis B. And then, you can wish for good luck or good genes, and thanks for listening to The Scope.
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