Colon Cancer: Etiology and Treatment (page 1 of 4)
By James P. Celebrezze Jr., M.D.
Division of Colon and Rectal Surgery

No one cause for the development of colon cancer has been identified. In general, polyps are
the precursors to colon cancer but again, their cause has many factors and is not completely understood. Many risk factors have been identified, such as age, family history and the presence of inflammatory bowel disease. Diet, environmental exposures, smoking and alcohol consumption also may play a role in the development of polyps and subsequent cancer. Without a clear-cut cause, prevention becomes difficult. Therefore, current techniques of prevention center on screening. While some colon cancers do occur as the result of a hereditary syndrome, the vast majority develop randomly without a clear family history.

That means no specific hereditary genetic defect can be identified. Even in young patients, the vast majority of cancers occur sporadically. As mentioned previously, age is a risk factor, with the incidence of polyps (and therefore cancer) increasing in the sixth and seventh decades of life. Family history is important, with risk increasing two to four times if first degree (ie. mother, father, brother or sister) relatives have been affected by colon cancer.

Treatment of Colon Cancer

In order to cure colon cancer, removal of the tumor is required. Colon cancers can present at various stages, ranging from malignant cells in polyps to diffusely metastatic disease. Currently, the AJCC TNM staging system is most commonly utilized in the staging and determination of treatment for colon cancer. As previously stated, the majority of colon cancers develop from polyps via the polyp to carcinoma sequence. This process generally takes years and involves several changes in the genes of the cells that line the colon. Polyps, if detected, polyps can be removed at any point along this sequence. No one can predict whether any particular polyp will become malignant, but the risk per polyp is estimated at 10 percent. One risk factor for the development of malignant degeneration is the size of the adenomatous polyp, with 1 cm polyps having a 10 percent incidence of containing malignant cells. For the reasons just stated, it is recommended that all adenomatous polyps be removed or eradicated in order to prevent malignant degeneration. If a polyp is removed and — upon pathologic evaluation — found to have malignant cells within, several factors become important in determining whether subsequent therapy is necessary or whether just removing the polyp is curative.