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Colon Cancer

Colon cancer accounts for nearly 98% of the malignant tumors arising in the colon and rectum. The three most common nonadenocarcinoma cancers at these anatomic sites are carcinoids, lymphomas, and sarcomas. The colon and rectum can also be the site of metastatic cancer and a variety of benign tumors, the most common of which is the adenomatous polyp. This article focuses on adenocarcinoma of the colon and rectum, commonly called colorectal cancer. The most frequent cancers in patients in the United States and most Western countries are cancers of the breast, lung, colon, rectum, and prostate. The number of new colorectal cancer cases in the United States in 1998 will be 135,000, and the number of deaths 50,000, making colorectal cancer the second leading cause of cancer death in the United States after lung cancer. The incidence of and death rate from this cancer are the same for women as for men. The mortality has been gradually colon cancer, colan, colen, canser


Adenocarcinoma of the colon is almost always preceded by a precursor lesion, the benign adenomatous polyp. The concept of the adenoma as a precursor of adenocarcinoma of the colon is strongly supported by epidemiologic and pathologic studies. In addition, clinical studies have provided evidence that polypectomy dramatically reduces the risk of subsequent colorectal cancer. Approximately two thirds of polyps encountered in the clinical setting are adenomas. These are classified histologically as

Colorectal cancer can be tiny to massive. The size is not predictive of metastatic potential. The tumors can be exophytic and polypoid with variable extension into the lumen or endophytic with little luminal involvement. The exophytic tumors can be broad based and sessile or, less commonly, pedunculated.


Surgical resection provides the best opportunity for cure. This can be done as the sole modality of treatment or in conjunction with radiation or chemotherapy. There is evidence that colon cancer involving lymph nodes is associated with better survival in patients who are treated with a course of postoperative chemotherapy with a combination of either 5-fluorouracil and levamisole (Ergamisol) or 5-fluorouracil and leucovorin (Wellcovorin). The survival of patients with rectal cancer that has


At the time of surgery, it will usually be clear whether the patient has gross residual disease after the resection. This will commonly be in the form of nodules on the liver or peritoneal surface that are too small to have been detected by preoperative imaging. A solitary implant or a small number of implants in the liver can be resected at that time or subsequently. A single pulmonary nodule is usually resected because it may be a new primary cancer of the lung rather than a metastatic focus from the colon. Residual disease after surgery may also be suspected if a preoperative CEA level has not fallen to normal in spite of the absence of gross residual disease observed at the time of surgery or on postoperative imaging.

Recurrent colon cancer is usually outside the bowel. Rarely, primary anastomotic recurrences are found after low anterior resections. Anastomotic recurrences are usually secondary to intra-abdominal recurrent tumor. Recurrent cancer that is nonresectable is usually treated with 5-fluorouracil, which is the most active agent, in combination with another agent, usually leucovorin. Other agents are used less successfully. Direct infusion into the liver of fluorodeoxyuridine (floxuridine, FUDR) has been shown to have significant response rates compared with systemic chemotherapy, but it is not clear whether it increases chances for survival. Radiation therapy is usually reserved for painful pelvic or bone disease and for the less common brain metastases. Patients who present initially with metastatic incurable disease may nevertheless have surgery offered, especially if the primary colon cancer is associated with bleeding or obstruction, provided that the patient has a reasonable performance status.