Approximately one in three persons in the United States will develop cancer within his or her lifetime, and roughly one in five will die of the disease. The estimated death rate in this country from cancer exceeds 500,000 per year and is surpassed only by deaths from cardiovascular diseases which accounts for 33.5% of all deaths annually. The incidence of cancer related deaths has doubled approximately every 30 years secondary to the aging of the population and the rapid rise in lung cancer. In contrast, the death rate from other disease processes has decreased over the past 20 years. During the period from 1967 to 1990, the death rate in this country from cancer rose from 16.8% to 23.5%. But what is cancer?
Cancer is a large complex group of diseases that begins at the cellular level of living organisms. The development of cancer is actually a rare event, considering the many billions of cells that comprise an organ of the body. One single cell can transform into a malignant cell, and through growth and replication, eventually produce the clinical disease we call cancer. Most cells in our body are differentiated, that is they have developed and matured into cells with a specific shape and function. During the process of differentiation into a mature functional cell, most normal cells lose their ability to proliferate. However, many tissues in our bodies undergo a constant process of renewal where the loss of mature cells is equally replaced by the production of less mature cells which then mature to perform their prescribed activities in the body. Most cancers probably originate from these immature cells known as precursor cells.
Evidence appears to show that cancers may arise from a single transformed precursor cell which then reproduces to form a group of malignant cells which eventually reaches a size which can be detected. These tumor cells possess the ability to alter and change their characteristics as they multiply however, and this can lead to a tumor with many different properties and activities.
In a normal environment, cell production is dictated by the death of older mature cells. However, in a malignant situation, cells are produced regardless of need, and tend to remain immature. Some cells can mature quite a bit, and this aids the pathologist in the diagnosis of the type of cancer.
Another property of cancer cells is their ability to spread to and invade other tissues of the body. Here they generate new tumors known as metastases. In almost all instances, this will decrease the ability to cure the cancer, thus making early detection our best weapon in the battle of cancer.