tailieunhanh - 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. | 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 stage-related 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 regional lymph node involvement. Prognosis may be more precisely gauged by the number of involved lymph nodes one to three lymph nodes versus four or more lymph nodes . A minimum of 12 sampled lymph nodes is thought necessary to accurately define tumor stage. Other predictors of a poor prognosis after a total surgical resection include tumor penetration through the bowel wall into pericolic fat poorly differentiated histology perforation and or tumor adherence to adjacent organs increasing the risk for an anatomically adjacent recurrence and venous invasion by tumor Table 87-6 . Regardless of the clinicopathologic stage a preoperative elevation of the plasma carcinoembryonic antigen CEA level predicts eventual tumor recurrence. The presence of aneuploidy and specific chromosomal deletions such as allelic loss in chromosome 18q involving the DCC gene in tumor cells appears to predict a higher risk for metastatic spread particularly in patients with stage II T3N0M0 disease. Conversely the detection of microsatellite instability in tumor tissue indicates a more favorable outcome. In contrast to most other cancers the prognosis in colorectal cancer is not influenced by the size of the primary lesion when adjusted for nodal involvement and histologic differentiation.