John is a seventy-year-old who has not been seen by his primary care physician for several years. He has noticed increasing fatigue and weight loss of about 10 pounds in the last two months. He is concerned that he may have seen signs of rectal bleeding in the past year (but attributed them to hemorrhoids). The physician orders a stool blood test, which is positive and detects iron deficiency anemia. John also has a moderate elevation in blood CEA levels. The physician notes that John has not had any of the recommended screening procedures for the detection of colorectal cancer such as colonoscopy or flexible sigmoidoscopy and is concerned about the possibility of such. John is unaware of any history of colorectal cancer in his large number of relatives. The patient is scheduled for colonoscopy, to which he objects, but the physician notes that other diagnostic procedures such as a double contrast barium enema or CT-based colonography also require preliminary bowel preparation and are likely to require subsequent colonoscopy either for definitive diagnosis or therapy. John undergoes successful colonoscopy during which several small polyps are found in the descending colon and removed. However, the endoscopist is unable to fully examine the colon because the lumen of the colon is stenosed (constricted) in the ascending portion, preventing further passage of the scope. The stenosed area appears to be associated with a large tumor that cannot be removed using the endoscope. The endoscopist tattoos the area with ink to note the area of concern and refers the patient for surgery. The surgeon notes a suspicious lesion of the right (ascending colon) and performs a right hemicolectomy, removing the lesion and the right colon, reattaching the small intestine to the transverse colon to preserve bowel function. During surgery, the surgeon also removes adjacent lymph nodes for analysis. The surgical specimen and nodes are sent to pathology for evaluation (FIGURE 7-19). Microscopic analysis indicates the lesion to be an adenocarcinoma that has infiltrated through almost the entire colon (FIGURE 7-20). No tumor is detected in lymph nodes. John is given a course of adjuvant chemotherapy with a cytotoxic agent. The patient remains healthy. His CEA level fell to normal and has shown no elevation in the five years since surgery.
FIGURE 7-19
FIGURE 7-20
Discussion
John is lucky. The only potential cure for colon cancer is surgical removal of the lesion. TMN analysis of his lesion would be T3; cancer has grown through the muscular layers but has not penetrated beyond the outer layer, or serosa, of the colon. N0 (no cancer in adjacent nodes), and M0 (no distant spread). T3N0 disease has almost an 80 percent five-year relapse-free survival rate. Adjuvant chemotherapy is not always used with John’s stage of disease but is likely to improve relapse-free survival. However, there is a moral to this case. It is extremely likely that John would never have had colon cancer had he followed routine cancer screening guidelines. Colon cancer peaks in both sexes at about age sixty-five. Hence, screening for polyps in the colon and rectum should start at age fifty (in the absence of other risk factors such as a strong family history or a defined hereditary disease). Because most colon cancer starts as a detectable precancerous lesion, removal of these lesions (colon and rectal adenomatous polyps) via endoscopy prevents colon cancer from occurring. Even removal of lesions showing marked dysplasia or localized cancer is likely to be curative. Because colon cancer progresses slowly, screening tests need not be undertaken frequently if no suspicious lesions are found. Colonoscopy at ten-year intervals allows examination of the entire colon and cecum and is considered to be the most sensitive screening test. It also allows for therapeutic removal of lesions. Alternatively, flexible proctosigmoidoscopy every five years is recommended. This procedure (unlike colonoscopy) generally does not require anesthesia and is often done by a trained physician rather than a gastroenterologist. It is less costly than colonoscopy and requires less patient preparation (generally two disposable enemas as opposed to the thorough bowel cleaning needed for colonoscopy). However, proctosigmoidoscopy (as the name implies) can examine only the descending colon. Detection of multiple polyps in this region suggests the presence of additional undetected polyps in the transverse or ascending colon, necessitating colonoscopy. Several other techniques are available for use in special cases (CT-based colonography, double contrast barium enema, and, recently, examination of the colon by orally ingested camera-containing capsules). None of these techniques allow for removal of lesions, and suspicious findings require follow-up colonoscopy. Annual fecal blood testing and tests that detect DNA mutations in the stool that derive from colonic cells may also be of value.
Questions
1. There is dispute over the cost effectiveness of colonoscopy versus proctosigmoidoscopy. What factors should be taken into account in establishing the procedure that should be recommended?
2. Stool-based DNA testing has been licensed for use in the detection of colon cancer. What potential advantages and disadvantages does such a test have?
3. There is some controversy about the use of adjuvant chemotherapy in this patient’s disease. What factors might argue for and against its use?