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Cancer is a group of more than 100 different diseases characterized by the uncontrolled, abnormal growth of cells. These cells form a lump or mass called a tumor. Some cancers, however, such as blood cancers, do not form tumors. Tumors can be benign (noncancerous) or malignant (cancerous). Benign tumors may grow, but they do not spread to other parts of the body and are usually not life threatening. Malignant tumors grow and invade other tissues in the body.
Sometimes cancer will spread to the lymph nodes. Lymph nodes are tiny, bean-shaped structures that filter the flow of lymph, the clear fluid that plays a role in the body's immune system. Lymph nodes are located in clusters in different parts of the body, such as the neck, groin area, and under the arms. Cells from malignant tumors can also break away and travel to other parts of the body, where they can continue to grow. This process is called metastasis. Metastatic cancer is named for the part of the body where it started. For example, if breast cancer spreads to the lungs, it is called metastatic breast cancer, not lung cancer.
Cancer can begin almost anywhere in the body. Tumors are named for the type of cell where the cancer started. For example, carcinomas begin in the skin or tissue that covers the surface of internal organs and glands. Sarcomas begin in the connective tissue, such as muscle, fat, cartilage, or bone. Refer to individual Cancer Type sections for more information.
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The American Cancer Society estimates that about one-third of the deaths from cancer can be prevented, as they are related to lifestyle factors such as diet, obesity, and lack of physical activity. In addition, 30% of cancer deaths this year are caused by tobacco use. Stopping smoking is the most important thing a person can do to lower his or her cancer risk. Although the risk of developing cancer can be greatly reduced by avoiding risk factors, not all cancers are preventable.
In some instances, the risk of developing cancer or of having cancer come back (recur) may be reduced by using drugs or other substances that lower the chance of developing cancer, called chemoprevention. Chemopreventive drugs include tamoxifen (Nolvadex), raloxifene (Evista), aromatase inhibitors, nonsteroidal anti-inflammatory drugs (such as aspirin), vitamins, and minerals. Many chemopreventive agents are still being studied, and the long-term effects are not yet well understood. Your doctor will be able to help you decide if chemopreventive drugs may be helpful in preventing cancer. Refer to individual Cancer Type sections for more information about the potential role of chemoprevention.
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The cause of cancer is largely unknown. Substances that are known to cause cancer, such as tobacco, are called carcinogens. Because it is often difficult to prove which substances actually cause cancer, scientists generally think that cancer results from a complex interaction of genetic and environmental factors. These factors can be described as external and internal.
- External factors include lifestyle choices, such as smoking cigarettes, chewing tobacco, being overweight or obese, and drinking alcohol; environmental causes, such as exposure to radiation and chemicals; and viral or bacterial infections that can damage cells and weaken the immune system.
- Internal factors include inherited (born with) genetic mutations and hormone exposure (such as estrogen).
Only 5% to 10% of cancers are hereditary. This means that a person inherited a gene from someone in the family that makes him or her more likely to develop cancer. Most people do not develop an inherited form of cancer; instead, a person’s genes become damaged by viruses, chemicals, sunlight, or tobacco use. These genetic changes are called acquired mutations, which usually take many years before they develop into a cancerous cell.
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A risk factor is anything that increases a person's chance of developing a disease such as cancer. People can control some risk factors, such as tobacco use. Other risk factors, such as age or ethnicity, cannot be controlled. Although risk factors can influence disease, for many risk factors, it is not known whether or not they actually cause the disease directly. Risk factors help doctors identify people who may be at higher risk of developing cancer.
Understanding your risk for cancer is important. People who have close relatives with cancer or close relatives who have died from cancer, especially at a younger age, may be at higher risk. For example, a woman whose mother or sister had breast cancer is twice as likely to develop breast cancer than a woman who does not have this same family history. People who have a history of cancer may benefit from screening tests at an earlier age or on a more frequent basis. People with a known genetic syndrome in the family may consider Genetic Testing. Your doctor or a genetic counselor can help you analyze your risk of developing cancer.
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| 5. Early detection and screening |
Cancer treatment is more likely to be successful when the cancer is diagnosed before it has spread. For many types of cancer, regular screening tests can help detect cancer early.
Currently, doctors can screen for cancers of the breast, colon, rectum, cervix, prostate, testes, mouth and mouth area, and skin. Screening tests for other cancers, such as lung and ovarian cancer, are currently being evaluated. Self-examination is also recommended for breast, skin, and testicular cancers, among others.
To determine which tests are most appropriate for each person, the doctor will consider a person's age, family history of cancer, ethnicity, and lifestyle. People at high risk for developing cancer should talk with their doctor about starting regular screening.
Read more about Understanding Cancer Screening.
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| 6. Tests to diagnose cancer |
Doctors use many different types of tests to diagnose cancer and to find out how far the disease has spread. Some tests can also determine which treatments will work best for a particular person. Diagnostic tests can involve simple laboratory tests, surgery, or radiologic imaging. The tests a doctor selects depends on the type of cancer that is suspected; the person's symptoms, age, and medical condition; and the results of other tests.
Biopsy. In many cases, a diagnosis of cancer is made with a biopsy. This test involves the doctor removing all or part of the tumor and then examining the sample under the microscope to determine if cancer cells are present. There are different kinds of biopsies.
Surgical biopsy. The doctor removes part of the lump (incisional biopsy) or the entire tumor or organ (excisional biopsy).
Fine needle biopsy. The doctor numbs the skin and removes a small sample of tissue with a thin needle.
Bone marrow biopsy. The doctor removes a sample of bone marrow, usually from the back of the hip, with a syringe.
Read more about What is a Biopsy? and Specimen Processing.
Imaging tests
Doctors use imaging tests to determine whether the cancer has spread to other areas in the body, and to evaluate the size and location of the tumor. Imaging tests alone are generally not specific enough to diagnose cancer.
X-ray. X-rays use electromagnetic radiation to produce an image of the inside of the body. X-rays are not as sophisticated as newer procedures, but they are still useful for finding and monitoring some types of tumors.
Computerized tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body using a series of x-ray pictures that are taken from many different angles. A computer compiles these images into a detailed, cross-sectional view.
Magnetic resonance imaging (MRI). An MRI uses electromagnetic waves to create computer-generated pictures of the inside of the body.
Ultrasound. Ultrasounds create pictures of the inside of body using high-frequency sound waves.
Positron emission tomography (PET) scan. This is a procedure in which radioactive sugar molecules, called tracers, are injected into the body in a low dose, radioactive form. During the scan, the cancer cells "light up," because the cancer cells absorb sugar faster than normal cells.
Bone scan. This test is used to determine if the bone is damaged, either from cancer or from some other cause. A radioactive tracer is injected into a person's body. If the bone is damaged, the tracer will concentrate in the bone.
Read more about Imaging Tests.
Endoscopic tests
Any medical procedure performed with an endoscope is called an endoscopy. An endoscope is a thin, flexible, lighted tube that is used to look at the inside of the body. The exact type of endoscope varies depending on what part of the body needs to be viewed. The following are some common examples of endoscopic tests.
- A bronchoscopy uses a bronchoscope to examine the lungs.
- A colonoscopy uses a colonoscope to examine the colon and rectum.
- A laparoscopy uses a laparoscope to examine the abdominal area.
Read more about Endoscopic Tests.
Laboratory tests
Laboratory tests involve testing a sample of blood, urine, and other body fluids to learn or confirm what is happening in the body. One of the most common tests is a complete blood count (CBC). A CBC measures the components of the blood, including white blood cells, red blood cells, and platelets. Blood tests are also used to monitor potential side effects of cancer treatment, such as anemia or infection.
Specific laboratory tests help doctors make treatment decisions. For example, the breast cells of women with breast cancer may be tested to determine whether the cells have the estrogen receptor, which lets doctors know whether these women will respond to hormone-based treatment. Also, the breast cancer drug trastuzumab (Herceptin) is only effective in people whose breast cells have a particular protein called HER2/neu. Some tests can be used to determine whether the cancer has returned, although this use differs for each cancer. Read the ASCO Patient Guide: Understanding Tumor Markers for Breast and Colorectal Cancers.
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Staging is the process of describing the size and location of the tumor(s) and whether the cancer has spread to other parts of the body. Staging is essential in determining the choice of therapy and assessing a person's prognosis (chance of recovery). Many diagnostic tests also help doctors to determine the stage of the cancer.
A number of different staging systems are currently used to classify tumors. For example, the TNM staging system, as proposed by the American Joint Committee on Cancer (AJCC), describes tumors in three ways: size of the primary tumor (T), absence or presence of cancer in the regional lymph nodes (N), and absence or presence of distant metastasis (M), or cancer that has spread to other areas of the body. Once the doctors determine the T, N, and M, they assign the cancer a stage. Stages are written as Roman numerals one through four (I, II, III, or IV).
Lower stage cancers are usually associated with a better prognosis; however, staging cannot be used to predict how long someone will live with cancer. Staging only provides a way of organizing information about a person's cancer so that doctors can better evaluate the treatment options.
A person may be diagnosed with stage 0 (zero) cancer, which means the cancer is confined to the place where it started and has not invaded any surrounding structures. Stage 0 cancer is also called cancer in situ. One example is DCIS of the breast, or ductal carcinoma in situ of the breast, that has not spread to any surrounding structures.
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The most common types of cancer treatment include surgery, radiation therapy, and chemotherapy. These therapies may be used either alone or in combination with other therapies. More recent treatment options include targeted therapies and biologic treatments. The first treatment that a person is given is called first-line therapy. Adjuvant therapy is treatment that is given after the first treatment (such as chemotherapy after surgery). Neoadjuvant therapy is treatment that is given before the primary treatment (such as hormone therapy before surgery). Most experimental therapies are tested in clinical trials.
As cancer care becomes more specialized, many people are now treated by a team of doctors, nurses, and other health-care specialists. Usually one doctor, often the medical oncologist, will help coordinate the person's care. Learn more about the Oncology Team.
Before beginning treatment, people should consider asking the doctor about the goals of treatment, how long the treatment will take, and the potential side effects. Read more Questions to Ask the Doctor.
It is also important that people with cancer and their families feel comfortable about their doctor and his or her recommended therapy. It is always appropriate to ask for a second opinion. Read more about Seeking a Second Opinion.
Surgery
Surgery involves the removal of cancerous tissue from the body. It is the primary treatment for many types of cancer, and some cancers can be cured with surgery. Surgery can also confirm a diagnosis (biopsy), determine how far a person's cancer has advanced (staging), relieve side effects (such as an obstruction), or ease pain (palliative surgery).
Some types of surgery can be performed in a clinic or doctor's office instead of the hospital. This is called outpatient surgery. Most cancer surgeries, though, will be performed in a hospital. Before surgery, consider preparing a list of questions for the surgeon. Carefully review with your doctor any preparation you may need before surgery.
The side effects of surgery depend on the type of surgery and the health of the person before surgery. One of the more common side effects is pain, which can be successfully treated in most people. Refer to individual Cancer Type sections for more information about surgical procedures for specific cancers.
Chemotherapy
Chemotherapy is the use of drugs to destroy cancer cells. Chemotherapy drugs fight cancer by interfering with the growth process of cancer cells, eventually causing the cells to die. Chemotherapy is used to shrink or eliminate the tumor, keep the tumor from spreading, destroy any cancer cells that have spread to other areas in the body, or relieve symptoms. Chemotherapy is called a systemic treatment, because it affects the entire body.
Chemotherapy is given by a medical oncologist, which is a doctor who specializes in treating cancer with medication. Some people may receive chemotherapy in their doctor's office; others may go to the hospital. A chemotherapy regimen usually consists of a specific number of cycles given over a period of time. Some drugs are given continuously over several days; some are given several times a week.
Side effects of chemotherapy
Chemotherapy can damage healthy cells along with cancer cells, which may cause side effects, including nausea, vomiting, and fatigue. Depending on the drug, some people may also experience tingling or numbness in the arms and legs, hair loss, and mouth sores. Because some drugs can damage blood cells, a person may experience anemia (low red blood cell counts) and/or an increased risk of infection (low white blood cell counts). Side effects can usually be treated and go away once treatment is finished. The occurrence of side effects is not related to whether the cancer drug is working or not.
During chemotherapy, a person may lose his or her appetite or develop an aversion to the taste or smell of food. Consider talking to a registered dietitian who can give suggestions about meal planning and managing side effects through simple diet changes.
Many people are concerned about the side effects of chemotherapy, and children and young adults should ask about long-term side effects of chemotherapy. Fortunately, many new drugs do not cause the same, severe side effects as some older chemotherapy drugs. And, there are many effective medications that help reduce side effects, caused by chemotherapy. Read more about Managing Side Effects.
Radiation treatment
Radiation therapy uses high-energy x-rays to destroy cancer cells. Radiation therapy is considered a local treatment, as it only affects one part of the body. The goals of radiation therapy include shrinking the tumor before surgery, keeping the tumor from returning after surgery, eliminating cancer cells in other parts of the body, and relieving pain (palliation).
Radiation therapy can be given two ways: externally and internally. With external-beam radiation therapy, a machine directs the radiation at the tumor from outside the body. With internal radiation therapy, also called brachytherapy, small tubes or implants (also called seeds) containing radioactive materials are placed in the body near the tumor. With internal radiation therapy, the person does not need to come to the hospital every day to be treated, and the doctor can use a higher dose of radiation. However, internal radiation therapy can only be used if the tumor is in a location where the doctor can place the implant.
Before beginning external-beam radiation therapy, the doctor will plan where to aim the radiation. The goal is to hit as much of the tumor as possible, while minimizing the exposure of healthy tissue. A person's skin may be marked to show where the radiation will be directed. New computerized techniques help pinpoint the best place to give the radiation.
Side effects of radiation treatment
Like chemotherapy, radiation therapy can also damage normal cells, causing side effects. These include tiredness (fatigue), swelling, redness or irritation of the skin, hair loss, cough or shortness of breath (if the radiation is given to the neck or chest area), mouth sores (if the radiation is given to the head), and digestive problems (if the radiation is given to the abdominal area). These side effects go away once treatment is finished. Internal radiation therapy may cause bleeding, infection, or irritation after the implant is removed. Radiation treatment does not make a person radioactive. Read more about Managing Side Effects.
External-beam radiation therapy may have long-term side effects that can affect a person for many years. For this reason, children and young adults who receive radiation therapy should keep a record of their radiation treatment schedule (including the dose and location of the radiation) and report it as part of their medical history. Long-term side effects can include the risk of a second cancer, the inability to have children (infertility), heart problems (from radiation to the chest), gastrointestinal problems (from radiation to the abdominal area), lung fibrosis (scarring or thickening of the lung tissue), neurologic problems, thyroid problems, or osteoporosis. Also, people who have had previous radiation to the chest should be aware that they are at higher risk of developing breast and lung cancers. Today, most people who receive radiation therapy now receive smaller doses than what was given in years past. Each individual considering radiation therapy should discuss the risks versus benefits of the treatment with his or her doctor.
Hormone therapy
Several types of cancer, including some breast and prostate cancers, can only grow and spread in the presence of natural chemicals in the body called hormones. Hormone therapy fights cancer by changing the amounts of hormones in the body, and is used to treat cancers of the prostate, breast, and reproductive system. For example, tamoxifen (Nolvadex) is an anti-estrogen drug used to treat some hormone-responsive breast cancers.
Hormone therapy does have potential side effects, but most side effects go away once treatment is finished. The side effects depend on the drug and affect men and women differently. Refer to individual Cancer Type sections for more information about hormone therapy and specific side effects.
Biologic therapy
Biologic therapy, also called immunotherapy, stimulates the disease-fighting mechanisms within the body to fight the cancer. Interferon and colony-stimulating factor are two examples of biologic therapy. These substances help restore functioning of the immune system. Researchers are developing specific types of biologic therapy, such as monoclonal antibodies and vaccines. The side effects of biologic therapy generally include flu-like symptoms, such as chills, nausea, and fever.
Monoclonal antibodies. Monoclonal antibodies are laboratory-produced substances that find and attach themselves to specific places on the surface of cancer cells. When they attach to a protein, they effectively stop the protein from doing its job (such as making cancer cells grow). For example, trastuzumab (Herceptin) is a monoclonal antibody therapy for breast cancers that have too much of a protein called HER2/neu. The antibody binds, or attaches to, the HER2/neu protein on the outer surface of tumor cells, preventing the growth and division of cancer cells. Other examples of monoclonal antibody therapies include cetuximab (Erbitux), rituximab (Rituxan), and bevacizumab (Avastin). Monoclonal antibodies can be used alone, in combination with other therapies, or to deliver drugs, toxins, or radioactive material.
Cancer vaccines. Cancer vaccines are another specific type of biologic therapy. Unlike vaccines that can prevent diseases such as chicken pox, cancer vaccines attempt to treat the cancer by training the immune system to recognize cancer cells and attack them. In some cases, doctors take tumor cells from the patient to make a vaccine. Cancer vaccines are being tested for many types of cancer, but are still highly experimental. Read more about Understanding Cancer Vaccines.
Targeted treatments
This general term describes drugs that "target" various proteins that can contribute to cancer. Unlike chemotherapy drugs that kill both healthy and cancerous cells, these drugs selectively kill cancer cells, which helps to reduce side effects. For example, imatinib mesylate (Gleevec) selectively blocks a protein that helps cancer cells grow. Other targeted treatments include gefitinib (Iressa) and erlotinib (Tarceva). Most targeted treatments are still experimental and are used along with other types of therapy. The benefits of these drugs can vary depending on a person's response to previous treatment and overall health. Generally, targeted treatments do not have the same side effects as traditional chemotherapy. Depending on the drug and the dosage, a person may experience nausea, vomiting, muscle cramps, rash, and/or diarrhea.
Anti-angiogenesis drugs. The formation of new blood vessels that feed tumors is known as angiogenesis. Some scientists think that by cutting off a tumor's blood supply, it may be possible to starve the tumor, and prevent it from growing and spreading. Anti-angiogenesis drugs are considered experimental at this time.
Antisense therapy. This therapy utilizes small, chemically-modified strands of DNA that block gene expression by binding to messenger RNA before it can produce a protein. Essentially, the technology acts to selectively "knock out" the production of a single protein.
Gene therapy. This therapy is used to repair or replace damaged genetic material or add new genetic material. Read more about Gene Therapy for Cancer.
Read more about Understanding Targeted Treatments.
Progress in cancer treatment continues to be made every day. Refer to individual Cancer Type sections for more information.
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