Almost half of all patients with colorectal cancer can be cured with surgery, the primary treatment method. Adjuvant chemotherapy can improve the survival for colorectal cancer. Adjuvant radiotherapy and chemotherapy can be used to improve survival for rectal cancer.
The chance for cure is clearly related to how far the tumor has invaded through the bowel wall and whether it has spread to the nearby lymph nodes . For those people whose lymph nodes are invaded by cancer, a major problem is that the tumor can come back after surgery. Recurrent cancer is the ultimate cause of death in one-third of cases.
Types Most colorectal cancers develop in the glands of the inner lining or mucosa and are called adenocarcinomas. Other kinds of tumors—lymphomas, melanomas and carcinoids—occur much less frequently.
How It Spreads Colorectal cancer spreads directly from the mucosa or inner lining through the muscle wall of the bowel and into adjacent tissues. The tumor may metastasize through the lymphatic system to nearby lymph nodes, to the liver through the portal vein and, less frequently, by the bloodstream to the bones or lungs.
What Causes It Environmental factors thought to contribute to the development of colorectal cancers include diet (high in saturated fat, low in fiber and possibly low in calcium) and lack of exercise. It is most common in industrialized countries with high standards of living. It is becoming more common in Japan as consumption of fats increases.
