Chapter 087. Gastrointestinal Tract Cancer (Part 12)

Most recurrences after a surgical resection of a large-bowel cancer occur within the first 4 years, making 5-year survival a fairly reliable indicator of cure. The likelihood for 5-year survival in patients with colorectal cancer is stagerelated (Fig. 87-3). That likelihood has improved during the past several decades when similar surgical stages have been compared. The most plausible explanation for this improvement is more thorough intraoperative and pathologic staging. In particular, more exacting attention to pathologic detail has revealed that the prognosis following the resection of a colorectal cancer is not related merely to the presence or absence of...
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Chapter 087. Gastrointestinal Tract Cancer (Part 12) Chapter 087. Gastrointestinal Tract Cancer (Part 12) Most recurrences after a surgical resection of a large-bowel cancer occurwithin the first 4 years, making 5-year survival a fairly reliable indicator of cure.The likelihood for 5-year survival in patients with colorectal cancer is stage-related (Fig. 87-3). That likelihood has improved during the past several decadeswhen similar surgical stages have been compared. The most plausible explanationfor this improvement is more thorough intraoperative and pathologic staging. Inparticular, more exacting attention to pathologic detail has revealed that theprognosis following the resection of a colorectal cancer is not related merely to thepresence or absence of regional lymph node involvement. Prognosis may be moreprecisely gauged by the number of involved lymph nodes (one to three lymphnodes versus four or more lymph nodes). A minimum of 12 sampled lymph nodesis thought necessary to accurately define tumor stage. Other predictors of a poorprognosis after a total surgical resection include tumor penetration through thebowel wall into pericolic fat, poorly differentiated histology, perforation and/ortumor adherence to adjacent organs (increasing the risk for an anatomicallyadjacent recurrence), and venous invasion by tumor (Table 87-6). Regardless ofthe clinicopathologic stage, a preoperative elevation of the plasmacarcinoembryonic antigen (CEA) level predicts eventual tumor recurrence. Thepresence of aneuploidy and specific chromosomal deletions, such as allelic loss inchromosome 18q (involving the DCC gene) in tumor cells, appears to predict ahigher risk for metastatic spread, particularly in patients with stage II (T 3N0M0)disease. Conversely, the detection of microsatellite instability in tumor tissueindicates a more favorable outcome. In contrast to most other cancers, theprognosis in colorectal cancer is not influenced by the size of the primary lesionwhen adjusted for nodal involvement and histologic differentiation. Table 87-6 Predictors of Poor Outcome Following Total SurgicalResection of Colorectal Cancer Tumor spread to regional lymph nodes Number of regional lymph nodes involved Tumor penetration through the bowel wall Poorly differentiated histology Perforation Tumor adherence to adjacent organs Venous invasion Preoperative elevation of CEA titer (>5.0 ng/mL) Aneuploidy Specific chromosomal deletion (e.g., allelic loss on chromosome 18q) Note: CEA, carcinoembryonic antigen. Cancers of the large bowel generally spread to regional lymph nodes or tothe liver via the portal venous circulation. The liver represents the most frequentvisceral site of metastasis; it is the initial site of distant spread in one-third ofrecurring colorectal cancers and is involved in more than two-thirds of suchpatients at the time of death. In general, colorectal cancer rarely spreads to thelungs, supraclavicular lymph nodes, bone, or brain without prior spread to theliver. A major exception to this rule occurs in patients having primary tumors inthe distal rectum, from which tumor cells may spread through the paravertebralvenous plexus, escaping the portal venous system and thereby reaching the lungsor supraclavicular lymph nodes without hepatic involvement. The median survivalafter the detection of distant metastases has ranged in the past from 6–9 months(hepatomegaly, abnormal liver chemistries) to 24–30 months (small liver noduleinitially identified by elevated CEA level and subsequent CT scan), but effectivesystemic therapy is improving the prognosis. Colorectal Cancer: Treatment Total resection of tumor is the optimal treatment when a malignant lesion isdetected in the large bowel. An evaluation for the presence of metastatic disease,including a thorough physical examination, chest radiograph, biochemicalassessment of liver function, and measurement of the plasma CEA level, should beperformed before surgery. When possible, a colonoscopy of the entire large bowelshould be performed to identify synchronous neoplasms and/or polyps. Thedetection of metastases should not preclude surgery in patients with tumor-relatedsymptoms such as gastrointestinal bleeding or obstruction, but it often prompts theuse of a less radical operative procedure. At the time of laparotomy, the entireperitoneal cavity should be examined, with thorough inspection of the liver, pelvis,and hemidiaphragm and careful palpation of the full length of the large bowel.Following recovery from a complete resection, patients should be observedcarefully for 5 years by semiannual physica ...