Cancer occurs when the cells in the body grow out of control. Healthy cells divide and grow in an organized manner. Cancer cells, on the other hand, continue to divide until they form a large mass called a tumor. This uncontrollable cell division occurs when a cell's DNA, which directs all of the cell’s activities, sustains unrepaired damage.

There are many different types of cancer, which typically begins in one part of the body, such as an organ (e.g., prostate) or tissue (e.g., breast).  If the disease is not detected and treated in its early stages, it can spread (metastasize) to other tissues and organs in the body. According to the American Cancer Society (ACS), cancer will affect about one out of every two men and one out of every three women in the United States at some point in their lives.

Though scientists do not understand exactly why DNA sustains damage, various factors have been identified that can increase an individual’s likelihood of developing cancer. These are called risk factors. Individuals who are aware of the risk factors associated with cancer can often prevent the disease by exercising certain cautionary measures, such as avoiding known carcinogens (cancer-causing agents).

Several elements can be examined to help identify a person’s risk of cancer. It is important to note that such measures do not mean an individual will develop cancer, only that there is greater susceptibility. Knowing the information can allow individuals to take preventive measures and be monitored by a physician. These factors include:

• An individual’s medical history. For example, hepatitis or cirrhosis may lead to liver cancer. Dialysis increases the risk of kidney cancer. Having an undescended testicle (cryptorchidism) raises a man’s chance of getting testicular cancer.
  
  
• Family history of hereditary cancer or syndromes. Certain cancers have stronger genetic links than others. Women who have a mother, sister or daughter with breast cancer have a greater risk for developing the disease. Also, certain syndromes can increase a person’s risk, such as familial adenomatous polyposis (FAP). Individuals with this condition are prone to colorectal cancer.

• Genetic testing. For example, having mutations of BRCA genes increases the risk of breast cancer in women and prostate cancer in men.

Preventive measures recommended by a physician depend on how much of an increased risk exists. For example, without treatment, people with FAP almost always develop colorectal cancer by age 40. Many of them undergo preventive removal of the colon (colectomy) to minimize this risk. Some women at high risk of breast cancer choose to have prophylactic mastectomy. In addition, women with breast cancer may be at increased risk to develop ovarian cancer. Breast cancer patients may choose to have their ovaries removed (oophorectomy) to prevent development of cancer there.

A physician may recommend increased monitoring rather than preventive treatments for people who face only a moderately increased risk of cancer. For example, a man susceptible to prostate cancer could undergo increased screenings with the digital rectal exam and  blood test for the tumor marker prostate-specific antigen. A woman susceptible to breast cancer could undergo mammograms with increased frequency at an earlier age or with increased frequency. The methods to monitor at-risk individuals for cancer are best determined by the patient’s physicians.