Before a true cancer develops, there often are earlier changes in the lining of the colon or rectum. One type of change is a growth of tissue called a polyp. Removing the polyp early may prevent it from becoming cancer. These are cancers of the cells that line the inside of the colon and rectum. There are some other, more rare, types of tumors of the colon and rectum.
Cancer can start in any of the four sections or where the colon ends in the rectum.
Colorectal cancer is the third most commonly diagnosed cancer in America. About 98,200 new cases of colon cancer and 37,200 new cases of rectal cancer will be diagnosed in 2001. The five-year survival rate is 90 percent for people whose colorectal cancer is found and treated in an early stage, before it has spread. But, only 37 percent of colorectal cancers are found at that early stage. Once the cancer has spread to nearby organs or lymph nodes, the five-year survival rate goes down to 65 percent.