Colorectal Adenocarcinoma

Radiologic-Pathologic Correlation

Abstract Introduction Etiologic and Growth Characteristics

Tumor Spread and Staging Role of Radiology Treatment and Follow-Up Prognosis

Conclusion Source Information References

Treatment and Follow-Up

Surgical resection of the primary tumor and the regional lymph nodes is the standard treatment for colon carcinoma. Surgical procedures include right and left hemicolectomies, the low anterior resection, and the abdominal-perineal resection. Right and left hemicolectomies entail surgical removal of a segment of the colon along a large vascular trunk, with eventual anastomosis of the proximal and distal excision sites. The low anterior resection is a transabdominal operation used for low sigmoid or high rectal carcinomas. The surgeon reaches down deep into the pelvis and removes the affected segment of bowel. At least 2 cm of rectum must remain to anastomose the colon (59,60). In the abdominal-perineal resection, both transabdominal and transrectal approaches are used for removing low rectal carcinomas. Because no anastomosis is possible with this operation, a colostomy is created. Both the low anterior resection and the abdominal-perineal resection entail manipulation of the presacral space, which is an important site of fibrotic changes as well as recurrent tumor.

In addition to surgery, adjuvant chemotherapy with fluorouracil/levamisole or with one of the other regimens now being studied in clinical trials should be considered for patients with stage II disease (61). Patients with stage III colon cancer should be offered adjuvant chemotherapy only in the context of a clinical trial, since their 5-year survival rate is up to 75% and since nearly half of the deaths of these patients are due to causes other than cancer (62). There is no standard chemotherapy for patients with widespread metastatic disease. Patients with stage I disease require surgical resection only: Local surgical excision or polypectomy is adequate treatment.

The evaluation and treatment for recurrent disease is important. One-third of patients who undergo surgery for colorectal carcinoma will develop recurrent disease. In 70%-80% of these patients, the cancer recurs within 2 years. Local recurrence is seen in approximately 60% of cases, distant metastasis in 26%, and a combination of both in approximately 14% of cases (43,45,47,58,63).

Both air contrast barium enema examinations and CT may demonstrate local recurrence, but CT alone can depict serosal, mesenteric, or distant tumor metastasis (Figure 16). The detection of an enlarging or globular soft-tissue mass is suggestive of recurrent disease, and biopsy and possibly a second operation may be required (64,65). The present recommendation for follow-up of colorectal carcinoma is to obtain a baseline CT scan at approximately 3 months after surgery and a follow-up scan every 6 months for 3 years (44).

MR imaging, like CT, is accurate in detecting masses following colorectal surgery but is not tissue specific (Figure 17). Initial reports were enthusiastic about the ability of MR imaging to allow differentiation of fibrosis from tumor, but later studies demonstrated that recurrent disease could not be reliably distinguished from fibrosis or radiation changes on the basis of increased signal intensity on T2-weighted images (66,67,68,69). Conversely, low signal intensity may be seen on T2-weighted images in areas of recurrent disease that are associated with marked desmoplasia. Biopsy is still needed to evaluate suspicious areas for recurrent tumor.

The presence of CEA in the blood of patients with cancer of the gastrointestinal tract produces a serologic method for the detection of recurrent disease with a sensitivity and a specificity between 70% and 90%. A rise in the serum level of CEA precedes clinical recurrence by approximately 6 months. An early, rapid rise is frequently associated with diffuse dissemination of disease, whereas a late, slow rise is associated with a better surgical salvage rate. Although CEA screening has not been proved to change the overall survival of patients with colorectal carcinoma, it is frequently used by clinicians as a marker to further evaluate patients with cross-sectional imaging. Although CEA screening is useful in evaluating patients with recurrent disease, it is not a good method for detecting initial disease (70). It is particularly useful in the detection of recurrent disease in patients who had an elevated CEA level preoperatively that normalized after resection and subsequently increased.

Abstract Introduction Etiologic and Growth Characteristics

Tumor Spread and Staging Role of Radiology Treatment and Follow-Up Prognosis

Conclusion Source Information References