Cancer

What is cancer?

Cancer is a large group of diseases with one thing in common: They happen when normal cells become cancerous cells that multiply and spread. Your genes send instructions to your cells — like when to start and stop growing, for example. Normal cells follow these instructions, but cancer cells ignore them.

Cancer is the second most common cause of death in the U.S. But fewer people are dying of cancer now than 20 years ago. Early detection and innovative treatments are curing cancer and helping people with cancer live longer.

Types of cancer

There are over 100 types of cancer. Healthcare providers categorize them according to where they start in your body and the type of tissue they affect. There are three broad cancer classifications:

• Solid cancers: This is the most common type of cancer, making up about 80% to 90% of all cases. This includes carcinoma that forms in epithelial tissue (like your skin, breast, colon and lungs) and sarcoma that forms in bone and connective tissues.
• Blood cancers: These are cancers that start in your blood cells or lymphatic system. Examples include leukemia, lymphoma and multiple myeloma.
• Mixed: Cancers that involve two classifications or subtypes. Examples include carcinosarcoma and adenosquamous carcinoma.

How common is cancer?

Cancer is the second most common cause of death worldwide. Researchers estimate that in 2024, over 2 million people living in the U.S. will receive a cancer diagnosis, and over 611,000 people will die from the disease.

About 1 in 4 people will develop cancer at some point during their lifetime.

The most common cancers in the U.S. are:

• Breast cancer.
• Lung cancer.
• Prostate cancer.
• Colorectal cancer.
• Blood cancers.

Anyone can develop cancer, but cases vary based on race and sex. According to the 2022 Annual Report on Cancer, the disease:

• Affects slightly more people assigned male at birth (AMAB) than people assigned female at birth (AFAB).
• Affects people over 60 more than any other age group.
• Affects more Black men (AMAB) than people in other racial groups.
• Affects more women (AFAB) who are American Indian or Alaska Natives than people in other racial groups.

What are the symptoms of cancer?

Symptoms of cancer vary from person to person. They depend on what type of cancer you have and how advanced it is.

General cancer symptoms may include:

• Fatigue.
• Fever that occurs mostly at night.
• Loss of appetite.
• Night sweats.
• Persistent pain.
• Skin changes, particularly moles that change shape and size or new moles.
• Unexplained weight loss.

In some cases, cancer may cause organ-specific additional symptoms. This may include:

• Blood in your pee or stool.
• Change in the shape, color or size of skin mole.
• Coughing up blood.
• New lumps or bumps.

This isn’t an exhaustive list. And having these symptoms doesn’t necessarily mean you have cancer.

Cancer is a complicated disease. Different types cause different symptoms. It’s also possible to have cancer for years without knowing it. Other times, it can cause obvious symptoms that get worse very quickly.

A good rule of thumb is to let a healthcare provider know any time there’s a change in your body that lasts for more than two weeks.

What causes cancer?

Cancer is a genetic disorder. But that doesn’t necessarily mean it’s inherited. It happens when genes that manage cell activity mutate (change). They create abnormal cells that divide and multiply, eventually disrupting how your body works.

These cells create cancer clusters, or tumors. Cancerous cells may break away from tumors and travel to other areas of your body through your lymphatic system or bloodstream. (Healthcare providers call this metastasis.)

For example, a tumor in your breast may spread to your lungs, making it hard for you to breathe. In some types of blood cancer, your bone marrow makes abnormal blood cells that multiply uncontrollably. Eventually, the abnormal cells crowd out normal blood cells.

According to medical researchers, inherited genetic mutations (changes you can’t control) cause about 5% to 10% of all cancers. More often, cancer occurs as an acquired genetic mutation (change). That means it happens over the course of your life. Medical researchers have identified several risk factors that increase your chance of developing cancer.

Risk factors

There isn’t one single cause for cancer. Rather, certain things can increase your chance of developing it, like:

• Family history. If you have close biological family members (parents, siblings, grandparents) who have cancer, you have a higher risk of developing it.
• Smoking. Smoking tobacco or using e-cigarettes increases your chance of developing lung, esophageal, pancreatic and oral cancer.
• Environmental factors. Exposure to toxins in your environment, like asbestos, pesticides and radon, can eventually lead to cancer.
• Malnutrition. High-fat or high-sugar foods can increase your risk for many types of cancer. You’re also more vulnerable to disease if you don’t get enough physical activity.
• Hormone therapy. Women and people assigned female at birth (AFAB) taking hormone replacement therapy may have an increased risk for breast cancer and uterine cancer.
• Radiation exposure. Ultraviolet (UV) radiation from the sun significantly increases your risk of developing skin cancer. Over-exposure to radiation therapy can also be a risk factor.

How is cancer diagnosed?

Healthcare providers begin a cancer diagnosis by doing a complete physical examination. They’ll ask you to describe your symptoms and your family medical history. They may also need to do:

• Blood tests for cancer, which may include complete blood count (CBC), blood protein tests and tumor marker tests.
• Imaging tests like CT scans, MRI, ultrasound or iodine metaiodobenzylguanidine (MIGB).
• Biopsies, which could be surgical (with an incision) or nonsurgical (with a needle).
• Genetic testing for cancer to diagnose and plan treatment for inherited forms of cancer.

How is cancer stage determined?

Healthcare providers use cancer staging systems to plan treatment and develop a prognosis or expected outcome.

Most cancers have four stages. The specific stage is determined by a few different factors, including the tumor’s size and location.

Stage I-III (1-3) (early-stage or locally advanced) usually describes cancer when it has grown directly into surrounding tissue or has spread to nearby lymph nodes.

Stage IV (4) (or metastatic) means that cancer cells have spread to distant areas of your body through your bloodstream or lymphatic system.

How is cancer treated?

Healthcare providers may use several different treatments, sometimes combining treatments based on your situation. Common cancer treatments include:

• Surgery: Can remove cancerous tumors that haven’t spread.
• Chemotherapy: Destroys cancer cells with powerful drugs in pill form or intravenously (through a needle into a vein).
• Radiation therapy: Kills cancer cells with high dosages of radiation.
• Immunotherapy: Engages your immune system to fight the disease.
• Targeted therapy: Targets the genetic mutations (changes) that turn healthy cells into cancer cells.
• Hormone therapy: Blocks cancer-causing hormones. For example, people assigned male at birth who have prostate cancer might receive hormones to lower testosterone, which can contribute to prostate cancer.
• Bone marrow transplant: Replaces damaged blood stem cells with healthy ones.

Cancer treatments can cause several side effects. These side effects vary depending on which treatment you have and how your body tolerates it. If you develop side effects during your cancer treatment, let your healthcare provider know. They may be able to give you recommendations or medications that can help.

Can cancer be prevented?

You can’t always prevent cancer, especially when unavoidable risk factors cause it. But there are things you can do to lower your risk:

• If you smoke or use tobacco, try to stop. Ask a healthcare provider about smoking cessation programs that can help you quit tobacco.
• Follow a nutrition plan that’s healthy for you.
• Include physical activity in your daily routine.
• Avoid environmental toxins like asbestos and pesticides.
• Protect yourself against sun damage.
• Have regular cancer screenings.

What is the outlook for cancer?

You are unique, and so is your prognosis. Your healthcare providers will base your outlook on factors like:

• Your overall health.
• The type of cancer you have.
• The stage of your cancer.
• How you respond to treatment.

While there’s no single cure for cancer, some cancers respond well to treatment. Many people notice a reduction in their signs and symptoms. When this happens, healthcare providers call it remission. Partial remission is when you have fewer signs and symptoms. Complete remission is when you no longer experience symptoms at all.

Different cancers require different treatments, so outcomes vary. In general, people who receive their diagnosis and begin treatment before cancer spreads have a more positive outlook. But even if your cancer has spread beyond where it started, treatment can slow its growth, ease your symptoms, help you live longer and improve your quality of life.

What are cancer survival rates?

Survival rates are estimates based on the experiences of large groups of people with different kinds of cancer. Like prognoses, survival rates vary based on cancer type, stage and treatment.

It’s important to remember that survival rates are only estimates. They can’t tell you how long you’ll live or how your body will respond to certain treatments. Your healthcare provider can tell you more about survival rates and what they mean for you.

How do I take care of myself?

Self-care is an important part of living with cancer, and it looks different for everyone. Giving yourself some TLC when you need it can reduce stress and enrich your mental, emotional and spiritual well-being. The following are some self-care ideas:

• Explore art or music therapy.
• Find a support group so you can talk with others who are having similar experiences.
• Get a massage (but get the “OK” from your healthcare provider first).
• Meet with a nutritionist to develop a personalized plan.
• Practice yoga, meditation or other forms of mindfulness.
• Read a cherished book or watch a favorite movie.
• Rest whenever you need to, not just when you can.
• Set your own “visiting hours” so you can spend time with your loved ones and still protect your downtime.
• Talk with a therapist or counselor about the emotional impact of your illness.
• Write your thoughts in a journal.

Some of these things might not be your cup of tea, and that’s OK. The bottom line? Do things that bring you joy and satisfaction. Find meaningful ways to spend your time.

When should I see my healthcare provider?

Tell your healthcare provider about any issues you have while you’re undergoing cancer treatment, including any treatment side effects. In many cases, your oncologist can find ways to keep you more comfortable. Don’t hesitate to reach out if you’re not feeling well.

What questions should I ask my doctor?

Knowledge is power. If you have cancer, you’ll want to gather as much information as you can. Here are some questions to ask your healthcare provider:

• What type of cancer do I have?
• Has the cancer spread to other areas of my body?
• What are my chances of survival?
• Which treatments do you recommend?
• What are the risks and benefits of my treatment?
• How long will treatment take?
• Will I be able to work during cancer treatment?
• Will cancer treatment affect my fertility?
• Will I need to stay in the hospital for my treatment?
• Would a clinical trial be a good option for me?

A note from Cleveland Clinic

“You have cancer” may be one of the scariest things you’ll ever hear. Suddenly, everything seems so uncertain. You might feel sad, alone, frustrated or angry. Maybe you’re all these things at once. Or maybe you’re totally numb. Whatever you’re feeling is valid and OK.

How will this diagnosis change me? What will my life look like now? How long do I have to spend with my loved ones? If these are the questions running through your mind, you’re not alone. The day of your diagnosis, you became a cancer survivor — a member of a global community. You’ll meet many people on this journey. Lean on them and your loved ones for support. Your healthcare providers understand the gravity of this life-changing event — and they’re here to help in whatever ways you need.