Information provided by National Cancer Institute U. S. National Institutes of Health www.cancer.gov What Is Cancer? Cancer begins in cells, the building blocks that form tissues. Tissues make up the organs of the body. Normally, cells grow and divide to form new cells as the body needs them. When cells grow old, they die, and new cells take their place. Sometimes, this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. These extra cells can form a mass of tissue called a growth or tumor. Tumors can be benign or malignant: * Benign tumors are not cancer: o Benign tumors are rarely life-threatening. o Generally, benign tumors can be removed, and they usually do not grow back. o Cells from benign tumors do not invade the tissues around them. o Cells from benign tumors do not spread to other parts of the body. * Malignant tumors are cancer: o Malignant tumors are generally more serious than benign tumors. They may be life- threatening. o Malignant tumors often can be removed, but sometimes they grow back. o Cells from malignant tumors can invade and damage nearby tissues and organs. o Cells from malignant tumors can spread (metastasize) to other parts of the body. Cancer cells spread by breaking away from the original (primary) tumor and entering the bloodstream or lymphatic system. The cells can invade other organs, forming new tumors that damage these organs. The spread of cancer is called metastasis. Most cancers are named for where they start. For example, lung cancer starts in the lung, and breast cancer starts in the breast. Lymphoma is cancer that starts in the lymphatic system. And leukemia is cancer that starts in white blood cells (leukocytes). When cancer spreads and forms a new tumor in another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if prostate cancer spreads to the bones, the cancer cells in the bones are actually prostate cancer cells. The disease is metastatic prostate cancer, not bone cancer. For that reason, it is treated as prostate cancer, not bone cancer. Doctors sometimes call the new tumor "distant" or metastatic disease. Risk Factors Doctors often cannot explain why one person develops cancer and another does not. But research shows that certain risk factors increase the chance that a person will develop cancer. These are the most common risk factors for cancer: Growing older Certain hormones Tobacco Family history of cancer Sunlight Alcohol Ionizing radiation Poor diet, lack of physical activity, or being Certain chemicals and other substances overweight Some viruses and bacteria Many of these risk factors can be avoided. Others, such as family history, cannot be avoided. People can help protect themselves by staying away from known risk factors whenever possible. Lab Tests Tests of the blood, urine, or other fluids can help doctors make a diagnosis. These tests can show how well an organ (such as the kidney) is doing its job. Also, high amounts of some substances may be a sign of cancer. These substances are often called tumor markers. However, abnormal lab results are not a sure sign of cancer. Doctors cannot rely on lab tests alone to diagnose cancer. Imaging Procedure Imaging procedures create pictures of areas inside your body that help the doctor see whether a tumor is present. These pictures can be made in several ways such as X-rays, CT scans, PET scans, MRI’s, ultrasounds, and radionuclide scans. Biopsy In most cases, doctors need to do a biopsy to make a diagnosis of cancer. For a biopsy, the doctor removes a sample of tissue and sends it to a lab. A pathologist looks at the tissue under a microscope. The sample may be removed in several ways, such as through a needle or through incisions. Treatment Methods The treatment plan depends mainly on the type of cancer and the stage of the disease. Most treatment plans include surgery, radiation therapy, or chemotherapy. Some involve hormone therapy or biological therapy. In addition, stem cell transplantation may be used so that a patient can receive very high doses of chemotherapy or radiation therapy. Some cancers respond best to a single type of treatment. Others may respond best to a combination of treatments. Some treatments are focused on the specific area of the cancer while others focus on the entire body. Local therapy removes or destroys cancer in just one part of the body. Surgery to remove a tumor is local therapy. Radiation to shrink or destroy a tumor also is usually local therapy. Systemic therapy sends drugs or substances through the bloodstream to destroy cancer cells all over the body. It kills or slows the growth of cancer cells that may have spread beyond the original tumor. Chemotherapy, hormone therapy, and biological therapy are usually systemic therapy. Surgery In most cases, the surgeon removes the tumor and some tissue around it. Removing nearby tissue may help prevent the tumor from growing back. The surgeon may also remove some nearby lymph nodes. Radiation Therapy Radiation therapy (also called radiotherapy) uses high-energy rays to kill cancer cells. Doctors use several types of radiation therapy. Some people receive a combination of treatments: Chemotherapy Chemotherapy is the use of drugs that kill cancer cells. Most patients receive chemotherapy by mouth or through a vein. Either way, the drugs enter the bloodstream and can affect cancer cells all over the body. Hormone Therapy Some cancers need hormones to grow. Hormone therapy keeps cancer cells from getting or using the hormones they need. Biological Therapy Biological therapy is another type of systemic therapy. It helps the immune system (the body's natural defense system) fight cancer. For example, certain patients with bladder cancer receive BCG solution after surgery. The doctor uses a catheter to put the solution in the bladder. The solution contains live, weakened bacteria that stimulate the immune system to kill cancer cells. BCG can cause side effects. It can irritate the bladder. Some people may have nausea, a low- grade fever, or chills. Stem Cell Transplantation Transplantation of blood-forming stem cells enables patients to receive high doses of chemotherapy, radiation, or both. The high doses destroy both cancer cells and normal blood cells in the bone marrow. After the treatment, the patient receives healthy, blood-forming stem cells through a flexible tube placed in a large vein. New blood cells develop from the transplanted stem cells. Stem cells may be taken from the patient before the high-dose treatment, or they may come from another person. Patients stay in the hospital for this treatment.