Bowel cancer is difficult to diagnose at an early stage because patients are usually asymptomatic early in the disease process. Screening to detect polys and cancer is important for all those deemed to be at risk and for those over the age of 50. Diagnosis of bowel cancer in the older adult is especially challenging because many of the common changes of aging in the gastrointestinal tract can prevent early detection. For example, constipation, change in bowel patterns and fatigue may be inaccurately attributed to the aging process.
Approximately 50% of patients present with hepatic metastases or develop them during the course of disease. Because the protal vein drains blood supply from the colon, the liver is the most common site of metastasis for advanced disease. Isolated lung or liver metastases may be resected in later stage disease. As the disease progresses, patients may experience bowel obstruction. Widespread metastases to abdomen, lung or liver are often the cause of death.
Most cancers of the bowel are moderately or well-differentiated adenocarcinomas. These cancers usually develop as a result of progressive colonic polyp mutations. Screening for and removal of potentially malignant polyps can prevent development of metastatic disease. TNM staging has been modified to correspond with the Astler coller dukes system. This staging process evaluates the depth of bowel wall penetration by the tumor, lymph node involvement, and presence of distant metastasis. The accuracy of the staging in high risk stage II and III is associated with the number of nodes surgically removed. Staging ranges from stage I to stage IV, with overall survival declining from greater than 90% to less than 10% for stage IV disease.
A complete staging work up includes a physical exam, pathologic tissue review, colonoscopy, and baseline computed tomography of the chest, abdomen and pelvis, complete blood count, chemistry profile and carcinombryonic antigen determination.
For resectable bowel cancer surgery remains the standard treatment. Tumor location, blood supply, and lymph node patterns are the area of cancer determine the extent of resection. Examination of a minimum of 12 lymph nodes is necessary for accurate staging. Laparoscopic advances have allowed the use of minimally invasive surgical procedures of resect bowel cancers without increasing recurrence rates. Early mobility, return of pulmonary function, and decreased ileus and adhesion formation have made this procedure desirable for many patients, especially those with advancing age and comorbid illnesses. Surgical management of bowel cancer involves resection with preservation of anorectal sphincter function, and sexual and urinary function whenever possible.
The role of radiation therapy is not well defined for bowel cancer, but more studies are needed, as completed studies are under powered. Debate over the value of pre or post surgical radiation therapy for bowel cancer continues. Although pre operative and post operative radiotherapy has been shown to reduce local recurrence when compared to surgery alone, neither intervention resulted in a statistically significant improvement in overall survival. Pre operative chemoradiotheraphy doubled the rate of bowel sphincter sparing operations and lowered the rates of local recurrence, acute toxicity, and long term toxicity.
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