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What you need to know about cancer

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There’s a lot you can do to lower your cancer risk, even if you have a family history. Learn more about what causes it, the risk factors, the most common types and how to protect yourself.

It’s tempting to think that cancer is something that happens only to other people. And yet it’s something that millions of us experience first-hand. In fact, nearly 40% will get cancer someday.1

That may feel scary, but there’s a lot to be hopeful about. More lives are being saved for some forms of the disease. And as many as 42% of new cancers could be stopped before they get started.2 That number doesn’t include certain types of non-fatal skin cancer. But it’s still worth celebrating.

Also worth celebrating? Making the healthy changes today that can lower your risk. Here are the basics you need to know. And we’ve got plenty of info on the good-for-you habits that can help protect you.

What is cancer?

Cancer is a group of diseases that can affect any part of your body. It happens when abnormal cells grow out of control.

Your body is made up of cells that grow and multiply throughout your life. When your body is functioning normally, old, damaged or abnormal cells die. New cells take their place.

Yet there are times when something goes wrong in this process, according to the American Cancer Society.3 The cells that are supposed to die don’t. That’s when cancer starts. These cells start growing out of control and push out normal cells. Although some cancers stay where they started, others can spread to other parts of your body.

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What causes cancer?

We know cancer is caused by changes within your body’s cells. But the real question is this: What caused those cells to change in the first place? That’s a more difficult question to answer. And it’s especially hard because cancer is many different illnesses, says Francisco A. Garcia-Moreno, MD. He chairs the department of oncology and hematology at ProHEALTH, part of Optum, in New Hyde Park, New York. And those changes can be spurred by many different things.

Here are five factors linked to cancer:

Your genes

Your family history plays an important role in your health. If cancer runs in your family, you might have a higher risk of cancer. But it doesn’t mean you will get cancer.

Cancer requires two things to take hold: certain genes and some kind of trigger. “Those are usually your lifestyle choices,” says Isamettin A. Aral, MD. He’s the radiation oncology division chief at ProHealth, part of Optum, in Riverhead, New York. “Those factors can either turn on or turn off your genes.”

And if you’re not doing anything to wake up those genes, your risk may be relatively low.

Your habits

How you live your life can influence your odds, even if you don’t have a family history of cancer. Smoking, eating unhealthy foods, sitting too much and gaining extra weight can make it harder to fight off dangerous cells. 


Certain viruses, bacteria and other germs can cause cancer. In fact, about 15% to 20% of all cancers worldwide are linked to these causes, according to the American Cancer Society (ACS).4 For instance, human papillomaviruses (HPVs), a sexually transmitted infection (STI), can cause cervical cancer and cancers in the mouth and throat.


Cancer can be linked to numerous types of radiation. Radiation is a type of energy. It’s produced by the sun and tanning beds, x-rays and radon. Radon is a radioactive gas. It’s colorless and odorless. It can seep into homes or buildings through the foundation.


It’s hard to stay away from chemicals. They’re in household products, the air, soil and even in certain workplaces. But many of them are listed as known and probable cancer causers by global and national organizations. This list includes things like asbestos, benzene and formaldehyde.5

What are the risk factors for cancer?

A risk factor is something that raises your chances of getting a disease. When it comes to cancer, numerous risk factors have been identified. You can’t control all of them. But you can control some.

Here are the most common risk factors6:

  • Age
  • Cigarette smoking
  • Secondhand smoke
  • Excess body weight
  • Drinking alcohol
  • Eating red and processed meat
  • Not eating enough fruits and vegetables, fiber and calcium
  • Not getting enough physical activity
  • Sun exposure
  • Certain infections
  • Certain chemicals
  • Exposure to radiation

What lifestyle habits can help lower your risk of cancer?

How you live can play a major role in helping reduce your risk of cancer. Only 5% to 10% of all cancer cases are genetic.7

Here are six cancer-fighting habits worth adopting:

  1. If you smoke, stop. This is No. 1 on Dr. Garcia-Moreno’s list. Tobacco use causes 1 in 5 deaths in the U.S. every year, according to the ACS. That’s why it’s called the leading preventable cause of death.

    Smoking causes 20% of all cancers and 30% of all cancer deaths. What’s more, it’s linked to 80% of all lung cancers and 80% of all lung cancer deaths.8 (Shop for products that can help you quit.)

  2. Limit alcohol. The American Institute for Cancer Research (AICR) classifies alcohol as a carcinogen (something that can cause cancer). The group reports that it’s been linked to at least six different cancers.9

    Dr. Aral counsels his patients with cancer to cut back or stop drinking. It’s especially important for people with breast or prostate cancer. “Alcohol doesn’t get (turned) into anything that’s useful for your body,” he says.

    Not drinking is best. But if you are going to drink, stick to no more than two drinks a day if you’re a man or one drink a day if you’re a woman.

  3. Maintain a healthy weight. Extra pounds aren’t something many people associate with cancer. In fact, more than half of Americans aren’t aware of this fact, according to the AICR. But at least 13 different cancers are linked to weight.10 Together, they make up 40% of all cancer cases in this country.

  4. Eat a plant-based diet. Chalk up another benefit to eating more plants. The AICR recommends eating mainly whole grains, fruits and vegetables. At the same time, it says to eat less sugar and meat.11

  5. Exercise regularly. Moving more helps you fight off cancer, protect your heart and manage your weight, says Dr. Garcia-Moreno. The AICR says to aim for 30 minutes of physical activity five times a week.12 Jump-start your fitness routine with our 14-day challenge. 

  6. Protect yourself from the sun. Follow these tips from the Skin Cancer Foundation13:

    • Use 2 tablespoons of a non-aerosol broad-spectrum sunscreen with an SPF of 15 or higher on your entire body 30 minutes before going outside. Add more every two hours or after sweating a lot or swimming.
    • Stay indoors or seek shade between 10 a.m. and 4 p.m.
    • Skip tanning beds.
    • Wear broad-rimmed hats and UV-blocking sunglasses.

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What screenings or tests can help prevent and detect cancer?

Spotting cancer early is critical. The earlier you find it, the earlier you can treat it. That’s why screening tests are essential. Here’s what the American Cancer Society recommends for people with average risk14:

Breast cancer: Annual mammograms starting at age 45 (with the option to begin at age 40)

Cervical cancer: Pap test and/or HPV test every three to five years starting at age 25 (some other experts suggest starting as early as 2115)

Colorectal cancer: Stool tests and/or visual exams beginning at age 45

Lung cancer: Annual CT scan for high-risk people starting at age 50

Prostate cancer: Blood test and rectal exam starting at age 50 (ask your doctor how often)

Skin cancer: A full-body skin exam during annual checkups for children and adults. 

Other experts may have differing recommendations. That’s why you should always talk to your doctor about which screenings are right for you.

“We’re seeing increased success in managing cancer,” says Dr. Aral. “And I think a lot of it has to do with people using very effective screening tools. That’s a huge piece, from my perspective.”

For more information on how and when to get these lifesaving tests, visit Get Screened at cancerscreenweek.org, and talk to your doctor.

What are the most common types of cancer?

Skin cancer is the most common cancer in the U.S. Thankfully, it’s also one of the most preventable. The sun’s ultraviolet (UV) rays cause most skin cancers. That’s why sunscreen is so important. And not just on sunny days, explains Laurie J. Levine, MD. She’s a board-certified dermatologist and chair of dermatology at ProHEALTH, part of Optum, in New Hyde Park, New York.

“You should put on sunscreen every day as a part of your skin routine,” says Dr. Levine. “Even in the winter. Even on a rainy day. And no matter what color your skin is.” One sneaky spot that’s easy to miss? Your ears. “Yes, it’s a bit difficult to put sunscreen on your ears, but it’s an area we often find skin cancer.”

Annual skin checks with your dermatologist are ideal. But it’s also important to check your own skin every month. “You know best if something is new, itchy or changing,” says Dr. Levine.

As you check your skin, keep the ABCDE rule in mind:

A is for asymmetry. One half of the mole does not match the other.

B is for border. The edges of a mole are uneven, jagged or blurred.

C is for color. A mole is not a solid color but has patches of brown, black, red, pink or white.

D is for diameter. A spot is larger than 6mm across (about the size of a pencil eraser).

E is for evolution. A mole is changing in size, shape or color over time.

After skin cancer, the next most common is breast cancer. That’s followed by prostate and lung cancers. Other common ones include:

  • Bladder cancer
  • Colon and rectal cancer
  • Endometrial cancer
  • Kidney cancer
  • Leukemia (blood cancer)
  • Liver
  • Non-Hodgkin lymphoma
  • Pancreatic cancer
  • Thyroid cancer

What are some symptoms of cancer?

Symptoms of cancer will often depend on the specific cancer. But here are some of the common signs that you should pay attention to, according to the ACS:

  • Tiredness that doesn’t get better with rest
  • Unexplained weight loss or gain of 10 pounds or more
  • Eating issues like:
    • Not being hungry
    • Trouble swallowing
    • Belly pain, upset stomach or throwing up
  • Swelling or lumps in the body
  • Pain with a new or little-known reason that doesn’t go away or gets worse
  • Skin changes like a new mole or a change in an existing mole
  • A sore that doesn’t heal
  • A yellowish color to the skin or eyes
  • Hoarseness in your voice or a cough that lingers
  • Unusual bleeding or bruising without a reason
  • Lasting changes in bowel habits or in how your stools look
  • Bladder changes, like:
    • Pain when you pee
    • Blood in your urine
    • Needing to pee more or less often
  • Fever or night sweats
  • Ongoing headaches
  • Hearing or vision problems
  • Mouth changes like numbness, sores or bleeding

If you have any of these signs, see your doctor. The earlier you can spot cancer, the better your outcome may be. (If you need a new doctor, we can help.) 

How is cancer treated?

Treatment often depends on the type of cancer you have and how advanced it is. While some people may need only one type of treatment, others may need a combination of treatments.

Here are some of the common treatments, according to the National Cancer Institute:

Biomarker testing. This is a way to look for genes and other substances so that you and your doctor can choose a cancer treatment.

Chemotherapy. This type of medication can kill cancer cells.

Hormone therapy. This type of medication blocks certain chemicals in the body (hormones) that help breast and prostate cancer to grow.

Hyperthermia. In this treatment, your body tissue is heated to 113 °F to kill cancer cells. It leaves healthy tissue unharmed.

Immunotherapy. This therapy uses parts of a person’s own immune system to help fight cancer.

Photodynamic therapy: This therapy uses light to "turn on” the medicine that kills cancer cells.

Radiation therapy: This therapy uses radiation to kill cancer cells and shrink tumors.

Stem-cell transplant: This procedure restores certain cells in your body that have been destroyed by chemotherapy or radiation therapy.

Surgery: Doctors physically remove cancer from your body.

Targeted therapy: Drugs that work on certain proteins in your body that stop cancer from growing.

What is it like to live with cancer?

If you’ve never had cancer, you might wonder what it’s like to live with it.

“It’s going to be different for different people,” says Dr. Garcia-Moreno. “And it’s different for different illnesses.” Some people are flattened by a cancer diagnosis and struggle to live through it. Others accept it and do everything they can to improve their quality of life. The good news, though? “We’re getting better at understanding what causes certain cancers and how to treat them. That means that the outcomes and life for people with cancer keep improving.”

What is remission?

Remission means that the signs and symptoms of cancer have decreased or disappeared. It can last anywhere from weeks to years. Partial remission is when the cancer has shrunk and is being controlled, but you still have some signs and symptoms. Complete remission is when you have no signs or symptoms and cancer cells cannot be detected by tests.

“We’re getting into situations where perhaps we’re not able to cure an illness, but we’re able to control it,” says Dr. Garcia-Moreno. “There are so many new treatments that are changing the way we deal with cancer. It’s easy to only focus on a cure. But gaining control of these illnesses is a tremendous victory on our part.”



  1. National Cancer Institute. Cancer stat facts: Cancer of any site. Accessed June 27, 2022.
  2. American Cancer Society. Risk of dying from cancer continues to drop at an accelerated pace. January 12, 2022. Accessed May 31, 2022.
  3. American Cancer Society. What is cancer? Last revised February 14, 2022. Accessed June 17, 2022.
  4. American Cancer Society. Can infections cause cancer? Last revised July 11, 2016. Accessed May 31, 2022.
  5. National Cancer Institute. Cancer-causing substances in the environment. Last updated December 28, 2018. Accessed June 27, 2022.
  6. National Cancer Institute. Risk factors for cancer. Last updated December 23, 2015. Accessed May 31, 2022.
  7. National Cancer Institute. The genetics of cancer. Updated October 12, 2017. Accessed June 17, 2022.
  8. American Cancer Society. Health risks of smoking tobacco. October 28, 2020. Accessed May 31, 2022.
  9. American Institute for Cancer Research. Alcohol labeling. Accessed May 31, 2022.
  10. Centers for Disease Control and Prevention. Cancer and obesity. October 3, 2017. Accessed May 31, 2022.
  11. Physicians Committee for Responsible Medicine. Reducing cancer risk with plant-based diet. Accessed May 31, 2022.
  12. American Institute for Cancer Research. Be physically active as part of your everyday life — walk more and sit less. Accessed May 31, 2022.
  13. Skin Cancer Foundation. Skin cancer prevention. Accessed May 31, 2022.
  14. Cancer Screen Week. Cancer screening may help save lives. Accessed June 27, 2022
  15. U.S. Preventative Task Force. Preventative Services: A and B Grade Recommendations. Accessed November 29, 2022.

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