Colorectal Cancer

COLORECTAL CANCER

Tumors of the colon and rectum are relatively common; the col-orectal area (the colon and rectum combined) is now the third most common site of new cancer cases and deaths in the United States. Colorectal cancer is a disease of Western cultures; there were an estimated 148,300 new cases and 56,000 deaths from the disease in 2002 (American Cancer Society, 2002).

The incidence increases with age (the incidence is highest for people older than 85 years of age) and is higher for people with a family history of colon cancer and those with IBD or polyps. The exact cause of colon and rectal cancer is still unknown, but risk factors have been identified (Chart 38-7).

The distribution of cancer sites throughout the colon is shown in Figure 38-7 (Goldman, & Bennett, 2000). Changes in this dis-tribution have occurred in recent years. The incidence of cancer in the sigmoid and rectal areas has decreased, whereas the inci-dence of cancer in the cecum, ascending, and descending colon has increased.

Improved screening strategies have helped to reduce the num-ber of deaths in recent years. Of the more than 148,000 people diagnosed each year, fewer than half that number die annually (Beyers et al., 2001). Early diagnosis and prompt treatment could save almost three of every four people with colorectal cancer. If the disease is detected and treated at an early stage, the 5-year sur-vival rate is 90%, but only 34% of colorectal cancers are found at an early stage. Survival rates after late diagnosis are very low. Most people are asymptomatic for long periods and seek health care only when they notice a change in bowel habits or rectal bleed-ing. Prevention and early screening are key to detection and re-duction of mortality rates.

Pathophysiology

Cancer of the colon and rectum is predominantly (95%) ade-nocarcinoma (ie, arising from the epithelial lining of the intes-tine). It may start as a benign polyp but may become malignant, invade and destroy normal tissues, and extend into surrounding structures. Cancer cells may break away from the primarytumor and spread to other parts of the body (most often to the liver).

Clinical Manifestations

The symptoms are greatly determined by the location of the cancer, the stage of the disease, and the function of the intesti-nal segment in which it is located. The most common present-ing symptom is a change in bowel habits. The passage of blood in the stools is the second most common symptom. Symptoms may also include unexplained anemia, anorexia, weight loss, and fatigue.

The symptoms most commonly associated with right-sided le-sions are dull abdominal pain and melena (ie, black, tarry stools). The symptoms most commonly associated with left-sided lesions are those associated with obstruction (ie, abdominal pain and cramping, narrowing stools, constipation, and distention), as well as bright red blood in the stool. Symptoms associated with rectal lesions are tenesmus (ie, ineffective, painful straining at stool), rec-tal pain, the feeling of incomplete evacuation after a bowel move-ment, alternating constipation and diarrhea, and bloody stool.

Assessment and Diagnostic Findings

Along with an abdominal and rectal examination, the most im-portant diagnostic procedures for cancer of the colon are fecal oc-cult blood testing, barium enema, proctosigmoidoscopy, and colonoscopy. As many as 60% of colorectal cancer cases can be identified by sigmoidoscopy with biopsy or cytology smears (Yamada et al., 1999).

Carcinoembryonic antigen (CEA) studies may also be per-formed. Although CEA may not be a highly reliable indicator in diagnosing colon cancer because not all lesions secrete CEA, stud-ies show that CEA levels are reliable in predicting prognosis. With complete excision of the tumor, the elevated levels of CEA should return to normal within 48 hours. Elevations of CEA at a later date suggest recurrence (Yamada et al., 1999).

Complications

Tumor growth may cause partial or complete bowel obstruction. Extension of the tumor and ulceration into the surrounding blood vessels results in hemorrhage. Perforation, abscess formation, peri-tonitis, sepsis, and shock may occur.

Gerontologic Considerations

The incidence of carcinoma of the colon and rectum increases with age. These cancers are considered common malignancies in advanced age. Only prostate cancer and lung cancer in men exceed colorectal cancer. Among women, only breast cancer exceeds the incidence of colorectal cancer (Lueckenotte, 2000). Symptoms are often insidious. Cancer patients usually report fatigue, which is caused primarily by iron-deficiency anemia. In early stages, minor changes in bowel patterns and occasional bleeding may occur. The later symptoms most commonly reported by the elderly are abdominal pain, obstruction, tenesmus, and rectal bleeding.

Colon cancer in the elderly has been closely associated with di-etary carcinogens. Lack of fiber is a major causative factor because the passage of feces through the intestinal tract is prolonged, which extends exposure to possible carcinogens. Excess fat is be-lieved to alter bacterial flora and convert steroids into compounds that have carcinogenic properties.

Medical Management

The patient with symptoms of intestinal obstruction is treated with intravenous fluids and nasogastric suction. If there has been significant bleeding, blood component therapy may be required.

Treatment for colorectal cancer depends on the stage of the disease (Chart 38-8) and consists of surgery to remove the tumor, supportive therapy, and adjuvant therapy. Data demonstrate de-lays in tumor recurrence and increases in survival time for patients who receive some form of adjuvant therapy—chemotherapy, radiation therapy, immunotherapy, or multimodality therapy.

ADJUVANT THERAPY

The standard adjuvant therapy administered to patients with Dukes’ class C colon cancer is the 5-fluorouracil plus levamisole regimen (Wolfe, 2000). Patients with Dukes’ class B or C rectal cancer are given 5-fluorouracil and high doses of pelvic irradia-tion. Mitomycin is also used. Radiation therapy is used before, during, and after surgery to shrink the tumor, to achieve better results from surgery, and to reduce the risk of recurrence. For in-operative or unresectable tumors, irradiation is used to provide significant relief from symptoms. Intracavity and implantable devices are used to deliver radiation to the site. The response to adjuvant therapy varies.

SURGICAL MANAGEMENT

Surgery is the primary treatment for most colon and rectal can-cers. It may be curative or palliative. Advances in surgical tech-niques can enable the patient with cancer to have sphincter-saving devices that restore continuity of the GI tract (Tierney et al., 2000). The type of surgery recommended depends on the location and size of the tumor. Cancers limited to one site can be removed through the colonoscope. Laparoscopic colotomy with polypec-tomy minimizes the extent of surgery needed in some cases. A lap-aroscope is used as a guide in making an incision into the colon; the tumor mass is then excised. Use of the neodymium/yttrium-aluminum-garnet (Nd:YAG) laser has proved effective with some lesions as well. Bowel resection is indicated for most class A lesions and all class B and C lesions. Surgery is sometimes recommended for class D colon cancer, but the goal of surgery in this instance is palliative; if the tumor has spread and involves surrounding vital structures, it is considered nonresectable.

Surgical procedures include the following:

•        Segmental resection with anastomosis (ie, removal of the tumor and portions of the bowel on either side of the growth, as well as the blood vessels and lymphatic nodes) (Fig. 38-8).

•        Abdominoperineal resection with permanent sigmoid colos-tomy (ie, removal of the tumor and a portion of the sigmoid and all of the rectum and anal sphincter) (Fig. 38-9).

•        Temporary colostomy followed by segmental resection and anastomosis and subsequent reanastomosis of the colostomy, allowing initial bowel decompression and bowel preparation before resection

•        Permanent colostomy or ileostomy for palliation of unre-sectable obstructing lesions

•        Construction of a coloanal reservoir called a colonic J pouch is performed in two steps. A temporary loop ileostomy is constructed to divert intestinal flow, and the newly con-structed J pouch (made from 6 to 10 cm of colon) is re-attached to the anal stump. About 3 months after the initial stage, the ileostomy is reversed, and intestinal continuity is restored. The anal sphincter and therefore continence are preserved.

A colostomy is the surgical creation of an opening (ie, stoma) into the colon. It can be created as a temporary or permanent fecal diversion. It allows the drainage or evacuation of colon con-tents to the outside of the body. The consistency of the drainage is related to the placement of the colostomy, which is dictated by the location of the tumor and the extent of invasion into sur-rounding tissues (Fig. 38-10). With improved surgical tech-niques, colostomies are performed on fewer than one third of patients with colorectal cancer.

Gerontologic Considerations

The elderly are at increased risk for complications after surgery and may have difficulty managing colostomy care. They may have decreased vision, impaired hearing, and difficulty with fine motor coordination. It may be helpful for the patient to handle ostomy equipment and simulate cleaning the peristomal skin and irri-gating the stoma before surgery. Skin care is a major concern in the elderly ostomate because of the skin changes that occur with aging—the epithelial and subcutaneous fatty layers become thin, and the skin is irritated easily. To prevent skin breakdown, special attention is paid to skin cleansing and the proper fit of an appliance. Arteriosclerosis causes decreased blood flow to the wound and stoma site. As a result, transport of nutrients is de-layed, and healing time may be prolonged. Some patients have delayed elimination after irrigation because of decreased peristalsis and mucus production. Most patients require 6 months before they feel comfortable with their ostomy care.