What is Cancer

Key Facts:

  •  Cancer is a leading cause of death worldwide: it accounted for 7.6 million deaths (around 13% of all deaths) in 2007.
  •  Lung, stomach, liver, colon and breast cancer cause the most cancer deaths each year.
  •  The most frequent types of cancer differ between men and women.
  • More than 30% of cancer deaths can be prevented.
  • Tobacco use is the single most important risk factor for cancer.
  • Cancer arises from a change in one single cell. The change may be started by external agents or inherited genetic factors.
  • Deaths from cancer worldwide are projected to continue rising, with an estimated 12 million deaths in 2030. - World Health Organization
  • Luis Diaz of the John Hopkins Kimmel Cancer Institute reports that Cancer is a genetic disease resulting from a variety of mutations and alterations either inherited from our parents or, more commonly, acquired over time due to environmental exposures and behaviors, such as smoking and poor diet.
  • These alterations turn off important cell growth regulators allowing cells to continually divide unchecked, explains Luis Diaz, a clinician-scientist in Ludwig Center for Cancer Genetics. This type of cell is called a malignant or cancer cell.  Among the trillions of cells in the human body, inevitably everyone has some abnormal or atypical cells that possess some of the characteristics of cancer cells, most resolve themselves and never result in cancer, says Diaz.

Cancer is a class of diseases in which a group of cells display uncontrolled growth (division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood). These malignant properties of cancers differentiate them from benign tumors, which are self-limited, and do not invade or metastasize. Although most cancers form tumors, there are also different cancers like leukemia (cancer of the blood or bone marrow) that do not. People at all ages maybe affected by cancer; however, the risk for most types of cancer increases with age. Cancer caused about 13% of all human deaths in 2007 (7.6 million).

To be more specific, cancers are caused by abnormalities in the genetic material of the transformed cells. These abnormalities may be due to the effects of carcinogens, such as tobacco smoke, radiation, chemicals, or infectious agents. Other cancer-promoting genetic abnormalities may randomly occur through errors in DNA replication, or are inherited, and thus present in all cells from birth. The heritability of cancers is usually affected by complex interactions between carcinogens and the host’s genome.

Genetic abnormalities found in cancer typically affect two general classes of genes. Cancer-promoting oncogenes are typically activated in cancer cells, giving those cells new properties, such as hyperactive growth and division, protection against programmed cell death, loss of respect for normal tissue boundaries, and the ability to become established in diverse tissue environments. Tumor suppressor genes are then inactivated in cancer cells, resulting in the loss of normal functions in those cells, such as accurate DNA replication, control over the cell cycle, orientation and adhesion within tissues, and interaction with protective cells of the immune system.

Definitive diagnosis requires the histologic examination of a biopsy specimen, although the initial indication of malignancy can be symptomatic or radiographic imaging abnormalities. Most cancers can be treated and some forced into remission, depending on the specific type, location, and stage. Once diagnosed, cancer is usually treated with a combination of surgery, chemotherapy and radiotherapy. As research develops, treatments are becoming more specific for different varieties of cancer. There has been significant progress in the development of targeted therapy drugs that act specifically on detectable molecular abnormalities in certain tumors, and which minimize damage to normal cells. The prognosis of cancer patients is most influenced by the type of cancer, as well as the stage, or extent of the disease. In addition, histologic grading and the presence of specific molecular markers can also be useful in establishing prognosis, as well as in determining individual treatments.

Chemotherapy, in its most general sense, is the treatment of disease by chemicals especially by killing micro-organisms or cancerous cells. In popular usage, it refers to drugs used to treat cancer or the combination of these drugs into a standardized treatment regimen. Most commonly, chemotherapy acts by killing cells that divide rapidly, one of the main properties of most cancer cells. This means that it also harms cells that divide rapidly under normal circumstances: cells in the bone marrow, digestive tract and hair follicles; this results in the most common side effects of chemotherapy – decreased production of blood , inflammation of the lining of the digestive tract, and hair loss.