What is cancer?

According to the American Cancer Society, cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death. Although cancer is often referred to as a single condition, it actually consists of more than 100 different diseases.

Cancer can arise in many sites and behave differently depending on its organ of origin. Breast cancer, for example, has different characteristics than lung cancer. It is important to understand that cancer originating in one body organ takes its characteristics with it even if it spreads to another part of the body. For example, metastatic breast cancer in the lungs continues to behave like breast cancer when viewed under a microscope, and it continues to look like a cancer that originated in the breast.

Cancer types can be grouped into broader categories:

  • Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs.
  • Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
  • Leukemia - cancer that starts in blood-forming tissue, such as bone marrow, and produces large numbers of abnormal blood cells that enter the bloodstream.
  • Lymphoma and myeloma - cancers that begin in the cells of the immune system.
  • Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord.

What are the conventional treatments for cancer?

Cancer treatment can take many different forms, and it is always tailored to the individual patient. Treatment decisions depend on:

  • The type and location of cancer
  • The extent to which the cancer has already spread
  • The patient's age, sex, and general health status
  • The patient's personal treatment preferences

The conventional cancer treatment is to remove all or as much of the tumor as possible and prevent the recurrence or spread of the primary tumor.

The major types of treatment are listed below.

  • Surgery involves the removal of a visible tumor and is the most frequently used cancer treatment. It is most effective when a cancer is small and confined to one area of the body.
  • Radiation kills tumor cells. Radiation is used alone in cases where a tumor is unsuitable for surgery. More often, it is used in conjunction with surgery and chemotherapy.
  • Chemotherapy is the use of drugs to kill cancer cells. It destroys the hard-to-detect cancer cells that have spread and are circulating in the body. Chemotherapeutic drugs can be taken either orally or intravenously, and may be given alone or in conjunction with surgery, radiation, or both.
  • Immunotherapy uses the body's own immune system to destroy cancer cells. This form of treatment is being intensively studied in clinical trials and is not yet widely available to most cancer patients.
  • Hormone therapy is standard treatment for some types of cancers that are hormone-dependent and grow faster in the presence of particular hormones. These include cancer of the prostate, breast, and uterus. Hormone therapy involves blocking the production or action of these hormones. As a result, the growth of the tumor slows down and survival may be extended for several months or years.
  • Bone marrow transplantation is the removal of marrow from one person and the transplant of the blood-forming cells either to the same person or to someone else. Bone marrow transplantation, while not a therapy in itself, is often used to rescue a patient, by allowing those with cancer to undergo very aggressive therapy.