What is cancer?
The body is made up of many types of cells. Normally, cells grow, divide and then die.  Sometimes, cells mutate (change) and begin to grow and divide more quickly than normal cells. Rather than dying, these abnormal cells clump together to form tumors. If these tumors are cancerous (also called malignant tumors), they can invade and kill your body's healthy tissues.  From these tumors, cancer cells can metastasize (spread) and form new tumors in other parts of the body.
By contrast, noncancerous tumors (also called benign tumors) do not spread to other parts of the body.
There are many different types of cancer, but all cancers begin with abnormal cells growing out of control.  There are more than 100 different types of cancer.
The type of cancer is determined by what type of cells begin to grow abnormally and where in the body the abnormal growth occurs. The most common cancers in adults are skin cancer, lung cancer, colon cancer, rectal cancer, breast cancer, endometrial cancer, ovarian cancer and prostate cancer.
Causes & Risk Factors
Who is at risk for cancer?
Everyone has some risk for cancer. In the United States, cancer is likely to affect 1 in 2 men and 1 in 3 women at least once in their lifetime. The amount of risk you have depends on a number of factors. These factors include tobacco use, lifestyle choices (such as diet and exercise), family history and factors in your workplace and environment.
How do I know if I am at risk for cancer?
Talk to your doctor. Your doctor can help you understand your risk for cancer, especially if other members of your family have a history of cancer. Your doctor can also help you understand how your risk for cancer is affected by the following:
Using or having used tobacco products, such as cigarettes or chewing tobacco
Having eaten a diet high in fat for much of your life
Being exposed to chemicals that can cause cancer
Being at risk for skin cancer
Depending on your age and your risk factors, your doctor may begin screening you for certain types of cancer. Screening means looking for certain cancers before they cause any symptoms. Some doctors recommend that people who are at high risk or have a family history of cancer be screened more often, or at a younger age, than people who have average cancer risks. The recommendations for screening vary for different cancers.
How does smoking and other tobacco use affect my risk for cancer?
If you smoke, quitting smoking is the single most important thing you can do for your health. Cigarette smoking is a major cause of cancers of the lung, larynx (voice box), mouth and esophagus, and it can also contribute to cancers in other parts of the body.
According to the American Cancer Society, people who quit smoking at any age live longer than those who continue to smoke. For example, smokers who quit before age 50 have half the risk of dying within 15 years compared with those who continue smoking. And the more you smoke, the more damage you do. People who smoke 2 packs or more per day are nearly 20 times more likely to develop cancer than nonsmokers.
Other forms of tobacco can also cause cancer, such as cigars, chewing tobacco and snuff. If you use tobacco products and want to stop, talk to your family doctor. He or she can help you make a plan to quit.
How does my family history affect my risk for cancer?
Unfortunately, some types of cancer seem to run in families. People of a certain race or ethnic group may also have a higher risk of some kinds of cancer.
Your doctor will ask you whether other people in your family have had cancer. If someone in your immediate family (a parent, brother, sister or child) has had cancer, you probably are at higher risk for cancer, also.
You can't change your family history, but it helps to be aware of it. If you and your doctor know that cancer tends to run in your family, you can watch more closely for the early signs of the disease. For example, if you are a woman and have a family history of breast cancer, your doctor may want you to start having mammograms more often or at a younger age.
What about factors in my workplace or environment?
There may be substances in your surroundings that can cause cancer or put you at a higher risk of developing cancer. These can include dust and vapors in the air you breathe and chemicals that touch your skin. Exposure to the sun without protection can cause skin cancer and breathing tobacco smoke (by smoking yourself or by breathing secondhand smoke) puts you at risk of lung cancer and other types of cancers.
Ask your employer if there are any materials in your workplace that can cause cancer. These may include asbestos, solvents and chemicals used for manufacturing or cleaning, smoke or fumes from burning materials and many others. Your employer should have a material safety data sheet (MSDS) for each substance that could potentially damage your health. All employers are required by law to complete these forms and you have a right to see them. Your employer should also provide safety equipment, such as a mask and protective clothing, to help decrease your exposure to any harmful materials.
Take a look at the environments you spend time in outside your workplace, as well. Too much exposure to the sun can cause skin cancer, the most common form of cancer. Try to stay out of the sun as much as you can. If you must spend time in the sun, wear protective clothing and sunscreen with an SPF (sun protection factor) of at least 15.
Breathing in smoke from a cigarette, cigar or pipe (even if you're not the person who's smoking) causes damage to your body that can lead to cancer. If you smoke, you need to quit. If someone in your family smokes, offer to help him or her quit, or ask him or her to not smoke when you are around. Cigarette smoke that clings to surfaces like carpet or clothing can also pose a risk, especially for infants and toddlers.
Diagnosis & Tests
What screening tests should women have?
Increasing age is the most important risk factor for breast cancer for most women. To help find breast cancer early, your doctor may perform a clinical breast exam (where he or she checks your breasts for lumps). Discuss the benefits and harms of a clinical breast exam with your doctor.
A mammogram is a special type of low-radiation X-ray of the breast. If you are between the ages of 50 and 75, you should have a mammogram every 2 years. If you are at high risk for breast cancer, such as a history of breast cancer in your family, your doctor may want you to have mammograms more often or at a younger age than 50. The value of mammography for average-risk women in their 40s is controversial and you should discuss the pros and cons of this with your doctor to make a decision you are comfortable with.
During a Pap smear, your doctor takes a sample of cells from your cervix to be tested for cervical cancer. Unless your doctor suggests that you need one more often, you should have a Pap smear:
Every 3 years beginning at 21 years of age and continuing until 65 years of age
Within 3 years of when you start having sex if you are younger than 21 years of age
If you are between 30 and 65 years of age and you want to have Pap smears less often, talk to your doctor about combining a Pap smear with human papillomavirus (HPV) testing every 5 years
Certain things put you at higher or lower risk for cervical cancer. Your doctor will consider these when recommending how often you should have a Pap smear.
If you're older than 65 years of age, talk with your doctor about how often you need a Pap smear. If you've been having Pap smears regularly and they've been normal, you may not need to keep having them.
If you've had a hysterectomy with removal of your cervix, talk with your doctor about how often you need a Pap smear.
If you've never had a high-grade precancerous lesion or cervical cancer, ask your doctor how often you need a Pap smear.
What screening tests should men have?
To make a decision about screening for prostate cancer, first talk to your doctor about the pros and cons of screening. Factors such as family history, age and race play a part in the risk of prostate cancer.
The National Cancer Institute, the American Cancer Society, the U.S. Preventive Services Task Force and the American Academy of Family Physicians recommend that men talk to their doctors about screening and make a decision based on the risk and potential benefits of screening, as well as their own personal values and preferences.
If you decide to have screening, your doctor will order a blood test called the PSA test. PSA is short for prostate-specific antigen. Men who have prostate cancer may have a higher level of PSA in their blood. However, the PSA level can also be high because of less serious causes, such as infection.
The AAFP recommends against prostate-specific antigen (PSA)-based screening for prostate cancer.
Why is it important to find cancer early?
Some common cancers are easier to treat and cure if they are found early. If the tumor is found when it is still small and has not yet spread, curing the cancer can be easy. However, the longer the tumor goes unnoticed, the greater the chance that the cancer has spread. This usually makes treatment more difficult.
What are the different kinds of cancer treatment?
The three most common types of cancer treatment are surgery, radiotherapy and chemotherapy. Treatment is aimed at removing the cancer cells or destroying them with medicines or by other means.
Surgery is a way to physically remove the cancer. Surgery can be very successful in treating some kinds of cancer, but it isn't an option in all cases. If the cancer is in the form of a malignant tumor (a tumor that spreads) but the tumor is still in one place (localized), it may be possible to safely remove the tumor and any surrounding affected tissue. Surgery may not be possible if the cancer has spread to other areas of the body or if the tumor cannot be removed without damaging vital organs, such as the liver or brain.
Different types of surgery are used to remove cancer. Some of these include:
Laser surgery. Beams of light and sometimes heat from a laser are used to target and destroy cancer cells.
Laparoscopic surgery. Very small incisions are made in the body, and the doctor uses a tiny camera to see inside your body. The camera sends signals to a video screen so that your doctor can see the tumor and your organs. The doctor uses a surgical tool to remove the tumor.
Mohs’ surgery. Layers of cancer cells are removed one at a time. Each layer is examined before the doctor removes the next layer. In this way, only the diseased layers are removed and healthy tissue remains intact.
Cryosurgery. Cancer cells are frozen and destroyed using a very cold material, such as liquid nitrogen.
Radiotherapy uses radiation—in the form of a special kind of X-ray, gamma rays or electrons—to damage cancer cells so that they can't multiply. There is usually no pain during this kind of therapy. Depending on the area that is treated, side effects from radiation damage to normal tissues may occur. Your doctor can tell you what to expect. Radiotherapy is sometimes the only treatment needed, or it may be used with other therapies. A combination of surgery and radiotherapy may be used for tumors that grow in one place.
Chemotherapy uses medicines to attack the cancer cells. The word "chemotherapy" sometimes causes a lot of fear because the side effects can be severe. However, not all people experience severe side effects. The side effects of chemotherapy can often be treated with other medicines.
Chemotherapy is usually used when the cancer has spread to other areas in the body. Chemotherapy can also be used in combination with surgery and radiation. Sometimes the tumor is surgically removed and then chemotherapy is used to make sure any remaining cancer cells are killed.
Another kind of treatment is biological therapy (also called immunotherapy). This treatment is used to trigger the body's immune system to produce more white blood cells, called lymphocytes (say: limf-o-sites). Two kinds of lymphocytes can attack and kill cancer cells: T-cells and B-cells. Immunotherapy aims to boost the ability of the T-cell and B-cell lymphocytes to kill cancer. This kind of therapy can also be used in combination with surgery, radiation therapy or chemotherapy.
Hormone therapy is sometimes used to treat breast or prostate cancer, often in addition to chemotherapy or radiotherapy. Hormone therapy involves taking drugs that contain other hormones to block the effects of estrogen and testosterone, also hormones. These drugs are necessary because the hormone estrogen can make breast cancer tumors grow faster. Similarly, the hormone testosterone can make cancerous tumors in the prostate grow faster. In other cases, surgery to remove the ovaries or the testicles may be used. Removing these organs reduces the amount of estrogen or testosterone in the body.
Other specialized treatments may be available. Your doctor may talk to you about these treatments if they are an option for you.
How do I decide what treatment option to use?
Your doctor, or a team of doctors, will help you understand your options and will recommend options for treatment. You may not have a choice in the treatment. Many factors are involved, including the stage that your cancer is in, what organs are affected, and the type of cancer that you have. Some cancers, such as skin cancer, are easier to treat than others. Your age and health, as well as the potential side effects of treatment, may also be factors in how much control you have over your treatment plan.
You and your doctor will want to consider both the advantages and disadvantages of each therapy. In addition, you and your doctor will want to discuss alternative therapies in case your cancer doesn't respond to treatment.
What are clinical trials?
 Clinical trials are used to research new ways of treating people who have cancer. After a new medicine goes through many tests in the lab and on animals, it is tested on people who have cancer and volunteer to take part in a clinical trial. The trial helps doctors decide whether a medicine is safe and effective. It also helps determine the correct dosages that patients should receive.
Cancer trials are run differently than some other clinical trials. In other types of trials, patients taking new medicines are compared to patients who receive no medicine at all (called a placebo or "sugar pill"). It would not be ethical for doctors to give people who have cancer a sugar pill containing no medicine. So, cancer trials compare patients receiving a current medicine to patients receiving the new medicine. Doctors hope that the trial will reveal that the new medicine works better than the current one.
There are some advantages to taking part in a clinical trial. Patients who do participate may receive the newest and best medicines available. Also, patients are monitored very closely throughout the trial, so their overall health often benefits. In addition, patients who take part in a clinical trial may not have to pay for the medicine they receive. The company or organization that sponsors the trial will usually provide the medicine at no charge, and will pay for extra testing and doctor visits.
Clinical trials also come with some risks. The medicines you may receive in a clinical trial usually have not been approved by the U.S. Food and Drug Administration (FDA). The medicine may have unwanted side effects, or it may not work as well as doctors hope it will. You may have to commit more time to your treatment if you take part in a clinical trial, and you may have to have more frequent tests.
If you think you might want to take part in a clinical trial, talk to your doctor. He or she can tell you about the possible benefits and risks and can help you look for a trial. You may also want to check the National Cancer Institute's Web site (see "Other Organizations") for more information and a searchable list of clinical trials.
I sometimes don't understand what my doctor is saying. What do I do?
Tell your doctor that you don't understand. You need to be aware of what's going on at each stage of your treatment, including all the options ahead of you. Bring a close friend or relative to your appointments to act as a second set of ears and eyes on your behalf. Your companion can help advocate for you.
It may help to take notes during your appointments. Write down any questions that you want your doctor to answer. You can also record all of your conversations, and then make notes from the recording. It's important that you understand what your doctor tells you, and that your doctor is aware when you don't understand. Be honest with your doctor. Don’t hold back any information, even when answering questions about how you feel, physically or emotionally, or how well you understand what the doctor is saying.
Who does what in my treatment program?
Cancer treatment can be very complex. The kind of cancer you have, the stage that it's in, and the treatment program you go through affects the kinds of health care professionals you’ll see.
Your family physician may oversee your treatment and rehabilitation programs, and can help answer questions you have. Sometimes an oncologist may manage your treatment program, but your family physician may take over once therapy is completed. An oncologist is a doctor who specializes in treating people with cancer.
A surgeon may do the operation to remove as much cancerous tissue as possible. A pathologist will examine the tissue that is removed during a biopsy or surgery to check for signs of cancer. Radiation oncologists administer radiation treatment. The radiation oncologist is often helped by diagnostic radiologists, radiotherapy technologists and radiation physicists, who plan treatment and check the radiation dosages to ensure that treatment is as safe as possible.
Oncologists, family physicians and internists often prescribe chemotherapy medicines, hormones and other drugs. Laboratory technicians or nurses may draw your blood for tests.
Nutritionists evaluate your diet and help you plan your meals during and after treatment. Physical therapists can help you keep your muscle tone and restore your ability to move around if there are any changes to your body from treatment. Psychologists, psychotherapists and other counselors, such as clergy or social workers, can help you talk through your feelings and manage the emotional reactions to your cancer and cancer treatment. Pharmacists mix the complicated medications and check that you are getting the correct dosages.
Don't hesitate to talk to your doctor about any questions and concerns you have about your treatment. If something is on your mind, ask about it. By getting answers to your questions, you can become a more active participant in your care.
What can I do about side effects?
Cancer treatment affects every person differently. Some people have few side effects or even none at all. However, the side effects of cancer treatment make many people feel very sick.
Your doctor will tell you what kinds of side effects you might expect with your cancer treatment. He or she will also tell you which side effects are unusual and when you need to call the doctor's office.
Don't downplay your side effects. It's important to tell your doctor, members of your care team and the people around you how you are feeling. If you feel very sick, very tired or are in a lot of pain, your doctor may be able adjust your treatment or give you other medicine to help you feel better.
Will I lose my hair?
Radiotherapy to the head and some types of chemotherapy can cause people to lose their hair. Other types of treatment do not cause this side effect. If you're having chemotherapy, ask your doctor whether the drugs you're taking can cause hair loss. Losing your hair can be a difficult experience. If your doctor tells you this might happen, try to prepare yourself. Decide what you want to do if you start to lose your hair.
Some people who lose their hair during cancer treatment wear a wig or hairpiece. Others cover their heads with hats, scarves or turbans. Still others leave their heads uncovered. Do what feels right for you. Many people switch back and forth, depending on where they are, who they're with and what they're doing.
If you decide that you want to wear a wig or hairpiece, it's a good idea to pick one out before you start losing your hair. That way, you can match it to your natural hair color and texture. Some shops specialize in wigs and hairpieces for people who have cancer. You may also be able to order your wig or hairpiece over the Internet.
If you decide to shave your head or leave it uncovered, you will need to protect your skin with sunscreen, a hat or a scarf when you're outside.
If you do lose your hair during radiotherapy or chemotherapy, it will almost always grow back after you finish your treatment. However, it might be a different color or texture when it grows back.
What if I don't feel like eating?
You may not feel well enough to eat while you're getting cancer treatment. But it's important to eat as much as you feel you can. Food helps your body build new, healthy cells and also helps boost your energy level.
It may help to eat several small meals a day instead of 3 large ones. Try eating bland foods like saltine crackers, plain toast and broth. Sip water, juices and soda. Ask your doctor about whether you should take a nutritional supplement, such as Ensure. Avoid spicy foods or foods with strong odors if they make you feel nauseous. You may also find that it's easier to eat and drink lukewarm food and beverages.
Some people who have cancer (especially people who are being treated with chemotherapy) have problems with mouth soreness or sensitivity. This may make it even more difficult to eat. Try eating soft, bland food or cooked food that has been pureed in a blender. If sores develop in your mouth, tell your doctor. These sores can become infected and cause serious problems. You may want to drink through a straw to bypass mouth sores. Also, try rinsing your mouth with 1 teaspoon of baking soda dissolved in 8 ounces of water. This can help prevent mouth infections and help your mouth heal faster.
When you do feel like eating, try to get as much protein and as many calories as possible. Ask your doctor whether you need to add certain nutrients or types of food to your diet. Your doctor may want you to visit a nutritional counselor, who can help you figure out ways to get the right amount of protein, nutrients and calories. If you find you can't eat at all for more than 24 hours, talk to your doctor. He or she needs to know that you're not getting the nutrition you need.
Will I be able to work?
You may not know the answer to this question until after you've started your treatment. Some people find that the effects of cancer and its treatment make them feel so sick that they're not able to work at all. Others are able to maintain their normal schedule or adjust it to work around their treatment.
Working during treatment can help keep your mind on things other than your cancer. You may also feel better knowing that you're continuing your "normal" routine. Many people who decide to work during treatment also find that they receive a great deal of support from their employers and coworkers.
If you want to continue working during cancer treatment, explore ways to make the most of your time. Try scheduling treatments for the end of the week, so that you'll have the weekend to recover. Ask your employer about working part-time or working from home. If necessary, ask coworkers to assist you with some of your tasks or duties. They will probably be eager to help.
How will I feel emotionally during treatment?
It's normal to feel helpless, angry, scared and depressed during cancer treatment. You will probably feel all of these emotions and more while you're going through treatment. On some days, you may feel like the treatment is not worth it.
Try to find a support system that you can rely on during these times. Many people count on family members and friends for support. Other people prefer to talk to people who are also going through cancer treatment. Cancer support groups can help people who have cancer and their family members cope with the disease and its treatment. Your doctor can suggest ways to find a support group, or you may contact a local hospital or the local chapter of the American Cancer Society (check the phone book or visit their Web site). The National Cancer Institute is another resource for support group information. (See "Other Organizations.")
Keeping your mind active can also help. Try to stay busy by doing jigsaw or crossword puzzles, knitting, watching movies or playing games with friends and family. Exercise can help too, but only if you're feeling strong enough. Talk to your doctor about what physical activity is best for you.
Some research, as well as the experience of many people who have cancer and their doctors, shows that a positive outlook may improve the health of people who go through cancer treatment. This positive-thinking approach can include forming a mental picture of how well your treatment and your body's immune system are fighting the cancer (also called visualizing).
It's also important to talk to your doctor about your emotions. Depression is common during cancer treatment. If it is a problem for you, your doctor may be able to prescribe medicine to help you feel better.
Should I tell my doctor that I was treated for cancer as a child?
Yes, this information is important. Your doctor will want to know about any childhood cancer and treatment. The treatments for a childhood cancer can lead to problems later in life. These problems include obesity, brittle bones, depression, heart trouble, women's reproductive issues and a higher risk of other cancers. Up to 60% of childhood cancer survivors who are now adults have at least one ongoing or late-arising health problem.
You can work out a plan for follow-up with your family doctor. You may have to talk to your parents or your childhood doctors to get the best plan for your health care now.
What can I do to lower my risk of cancer?
Unfortunately, some risk factors for cancer (such as family history) are out of your control. But there are things you can do each day to improve your health and lower your risk of cancer. The best ways to lower your cancer risk are to stop smoking and to maintain a healthy weight, be active and eat a healthy diet. Limiting how much alcohol you drink is also important, as is limiting your exposure to sunlight or tanning beds. If you are a cancer survivor, these same lifestyle habits can help you stay healthy.
Seeing your doctor regularly can also help. Depending on your age and medical history, your doctor will probably run tests (called screenings) to try to detect the early signs of certain cancers. For most types of cancer, the sooner the cancer is found and treatment begins, the better your chances of recovering.
Why is my weight important?
Reaching and staying at a healthy weight lowers your risk of many different cancers. Maintaining a healthy weight will also help lower your risk of other conditions, such as heart disease and diabetes. Ask your doctor what a healthy weight would be for you. If you are above a healthy weight, even losing just 5 percent to 10 percent of your current weight can help your health.
Why is being active important?
Being active on a regular basis can lower your risk of several types of cancer, including colorectal cancer and breast cancer. Exercise helps strengthen bones, build muscle and reduce body fat. It can also help improve self-esteem, and increase heart and muscle strength. Regular physical activity is also important for cancer survivors because it can help reduce tiredness and stress.
Most adults can do moderate activity without checking with their doctor first. However, if you are a man older than 40 years of age or a woman older than 50 years of age, or if you are a cancer survivor, talk to your doctor before starting an exercise program.
Try to get at least 30 minutes of activity, 4 to 6 times per week. Try to keep a medium- to high-intensity level of activity. You can become more active by adding even a small amount of activity into your daily routine. For example, try taking the stairs rather than the elevator. Go for a walk during a coffee break or during lunch.