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Cancer Mythbusters: Cancer Genetics and Prevention

  • In this episode, we explore the myth that cancer is always inevitable — and that there's nothing we can do to prevent it from coming our way. With the help of Huma Q. Rana, MD, clinical director of the Center for Cancer Genetics and Prevention at Dana-Farber, we explore the relationship between genetics, cancer, and cancer risk, and address how our lifestyle choices affect our chances of developing cancer.

    Read the transcript:

    MEGAN: Hi, I'm Megan Riesz, and this is Cancer Mythbusters, a podcast from the Dana-Farber Cancer Institute about the many myths and misconceptions in the world of cancer. Every episode, we'll take a look at a myth and debunk it with the help of our world-leading clinicians and researchers.

    This might sound obvious, but it's worth saying: Cancer can be scary.

    It's a good bet that nearly everyone on the planet knows someone with cancer, knew someone with cancer, or has heard of someone with cancer. And as we know, not everyone survives.

    Thanks to research and new, effective treatments, survivorship is on the rise. The American Cancer Society estimates that the population of cancer survivors will increase from 15.5 million in 2016 to 20.3 million by 2026.

    But many people are still, understandably, afraid that they will develop cancer and that they have no power over whether it comes their way, which brings us to today's question:

    Are we really powerless to lessen our risk of developing cancer?

    Of course, most of us know that smoking can cause lung cancer and that too much sun exposure can develop into melanoma, but what about some of our other lifestyle choices? How much do they really matter?

    To help me get to the bottom of this, I sat down with Dr. Huma Rana, Clinical Director of Cancer Genetics and Prevention at Dana-Farber.

    MEGAN: Thanks for joining me, Dr. Rana.

    DR. RANA: Thanks for having me, Megan.

    MEGAN: Can you start off by explaining the relationship between genetics, cancer, and cancer risk?

    DR. RANA: Sure. First of all, it's important to understand that cancer cells and all of the cells of our body share roughly the same 22,000 genes. The difference between cancer cells and healthy cells is that cancer cells turn off genes that would regulate their growth, and they turn on genes that help them to grow or proliferate.

    When we talk about cancer genetics, we're talking about these two different types of genetics that are interrelated.

    One is the genetics of the tumor or the cancer—what's being turned on and what's being turned off.

    The second is our constitutional genetics, or our germline genetics—the genes that we're born with or that we've inherited from our parents.

    Most cancers are due to mutations that occur specifically within the group of the cells or the tissues that have cancer, and are not due to an inherited, genetic, germline susceptibility. The vast majority of cancer (about 90 percent) occur by chance due to what we call "sporadic mutations," and it's only five percent to 10 percent that are due to genes that we're born with.

    MEGAN: Some people seem to think that if they have a family history of cancer, there's nothing they can do to prevent cancer from coming their way. Can you tell us whether people can take concrete steps to lessen their likelihood of cancer if they know they have that family history?

    DR. RANA: Most people who have a family history of cancer are not at increased risk for developing cancers because most cancers aren't due to an inherited susceptibility. However, there are some families where there is a clear genetic susceptibility or inherited risk for cancer. Those are families that have things like Lynch Syndrome, or families with BRCA1 mutations, BRCA2 mutations, or Li-Fraumeni Syndrome. People from those families can undertake genetic testing to help clarify their risk and determine what cancers they're at increased risk for. If they have that genetic susceptibility to cancer, they would be screened differently. Often, those individuals are screened earlier than people in the general population; they're screened more frequently than people in the general population; and they're also screened with different tools than folks in the general population.

    MEGAN: In terms of cancer risk, we know that smoking can cause cancer and that sun exposure can cause cancer. These points seem to have been driven into the public psyche. But can factors like nutrition and exercise help prevent cancer, or is that a myth?

    DR. RANA: While there are well-established factors for cancers such as smoking, infections, and radiation, there are other things that have more subtle effects on cancer risk but absolutely are associated with cancer risk.

    For instance, there are studies that show being physically active is helpful in lowering risk for specific types of cancer, including colon cancers, breast cancers after menopause, and uterine (and endometrial) cancers.

    In addition, things like obesity are also linked to certain types of cancers — again, breast cancer after menopause, colon cancer risk, uterine cancer risk, cancers of the esophagus, kidney, and pancreas.

    MEGAN: Are there any lesser known cancer prevention tips that you think people might be surprised to hear?

    DR. RANA: That's a great question, Megan. While inflammation is part of the normal process that the body uses to heal, chronic inflammation from things like Inflammatory Bowel Disease is associated with an increased risk for certain cancers. I think some of the things that I talk about with my patients that they're often surprised to hear about are things like alcohol intake.

    Alcohol is a known carcinogen. It's associated with risk for head and neck cancers, esophageal cancers, liver cancer, breast cancer (which women are always surprised by), and colorectal cancer risk. Let's be clear — alcoholic beverages are carcinogenic to women and men, to all humans, and really, the more that one drinks, the higher the risk for specific cancers.

    MEGAN: What would you say to those people who have eaten healthy their entire lives, who haven't smoked, who have exercised, and who eventually develop cancer? Those people could conceivably argue that our myth — that there's nothing you can do to lessen your cancer risk —is true.

    DR. RANA: What I tell my patients is that you can do everything right and still develop cancer, which is unfortunate. There are a number of things that we can't modify. The most important risk factor for cancer is age. The older you get, the higher the risks become, and we can't turn back time. We can't modify our age. At this point in time, we can't modify our genes, although down the road, we may be able to. For women, we can't modify the age of one's first period or when you go through menopause. So, those people have a valid point. There are many things we can't modify, but I think that's why it's important that for all of the risk factors that we can modify that we do our due diligence. That includes:

    • Exercise
    • Maintaining a healthy body weight
    • And avoiding carcinogens because those overall have a profound effect on our health

    MEGAN: You touched on the fact that advancing age seems to be the most significant risk factor for cancer almost across the board. The National Cancer Institute says that the median age of a cancer diagnosis is 66 years old. For older folks with perhaps less mobility and more dietary restrictions, what are some easy ways to make those important lifestyle changes?

    DR. RANA: Any exercise that they can get is beneficial even if that is limited to walking. I think walking daily is great for one's health. It is cardiovascular exercise. If people have difficulty with mobility in walking, then things like swimming are also a great way to get cardiovascular exercise.

    In terms of diet, reducing red meat consumption to less than 2 servings per week — that's a clear way to reduce risk for colorectal cancers. Trying to consume vegetables, fruits, and things with high fiber is helpful, and also staying up to date on their cancer screening — mammograms, colonoscopies. That's all a recipe for trying to maintain one's health and to help to find cancers early or to prevent them.

    MEGAN: It seems like cancer screening recommendations are constantly changing, and they're different based on factors like your gender, your sexuality, and your medical history. For young adult men and women, what are some basic rules of thumb to consider when it comes to getting screened?

    DR. RANA: That's a great question, Megan. I think it's really important for young people to take ownership of their health. The first step to doing that is to get their family history. Talk to your parents, talk to your grandparents, talk to your aunts and uncles, and flesh out the family history.

    • Who had cancer?
    • How old were they when they had these cancers?
    • Did they have colorectal polyps on colonoscopies?
    • How frequently do they have to have screening?

    All of those questions and answers can put together a family picture and can result in identifying a pattern of specific cancers that may reflect that someone is at an increased risk for one of these genetic syndromes that causes a predisposition to cancer. I think that's the most important step.

    The second point is to avoid carcinogens:

    • Don't smoke. If you smoke, stop smoking.
    • Avoid alcohol, or avoid abusing alcohol, because alcohol is associated with a number of cancers, as we've already discussed.
    • Practice safe sex to reduce the risk of catching sexually transmitted infections. We know that HIV is associated with numerous cancers because it can suppress the immune system. Also, HPV causes cervical cancer, cancers of the oral pharynx, vaginal, vulvar, penile cancers. There's a vaccine for HPV that can be given until the age of 26.

    The third thing that young adults can do is embrace a healthy lifestyle. I always end my patient visits by telling people to exercise, exercise, exercise. I can't say that enough! Eat a healthy diet, and try to maintain a normal body weight.

    MEGAN: Thank you so much for joining us, Dr. Rana.

    DR. RANA: You're welcome. Thanks for having me, Megan.

    MEGAN: So, there you have it. Most people who have a family history of cancer do not have an increased risk of developing cancer, though people with a family history of conditions, like Lynch Syndrome or BRCA1 mutations, do have a higher inherited risk. Factors like alcohol intake, exercise, and red meat consumption can affect your chances of developing cancer, though some of the major risk factors for cancer, like age, are unchangeable.

    For medical treatment or answers to personal questions, we strongly encourage you to consult with a qualified healthcare provider. For advice about your own care, please ask your doctor.

    See all Cancer Mythbusters episodes

  • Cancer Genetics
  • Risk & Prevention