Colorectal Liver Metastases
Related narrative: Hepatic Resection for Metastatic Colon Carcinoma
The liver is the most common site of metastatic spread of colon cancer (50%) followed by lung (10%), bone (5%) and brain (<5%). At the time of discovery of colon cancer, 70% of patients have no clinical evidence of distant spread. Of those resected for cure, about 60% of Duke's stage C will have metachronous recurrence, usually (85%) within the first two years. Close surveillance (Q 3-6mo) is necessary following resection for colorectal cancer and includes hemoccult, labs, chest X-ray (Q 6 mo first year, then yearly), baseline CT 3-4 months post-op, yearly colonoscopy and frequent carcinoembryonic antigen (CEA) levels. The CEA will return to normal between 6 weeks and 4 months in most patients with complete resection of the primary cancer. Failure to do so usually indicates incomplete resection or recurrence. Local recurrence is usually associated with a slow rise in CEA, while liver and lung metastases cause a rapid increase. CEA levels are elevated in 80-90% of patients with liver metastases. Radioimmune guided surgery (RIGS), consisting of injecting monoclonal antibodies to CEA and reexploring six weeks later to detect occult metastases with a hand held gamma probe, is a promising adjunct in asymptomatic patients. PET scanning, based on increased uptake of tagged glucose in tumors also enhances early detection of recurrence. A small percent (10-15%) of patients with recurrent disease have only liver metastases.
The natural history of untreated Dukes D/TNM stage IV colorectal cancer is bleak, with a 60-75% mortality by 1 year and close to 100% at 3 years. The prognosis is inversely proportional to the extent of disease. Systemic chemotherapy or regional hepatic infusion of chemotherapeutic agents may offer a slight improvement with 5 year survival of 5%, but the best chance for increased survival and potential cure is surgery for selected patients with hepatic metastases.
Early experience with hepatic resection for limited isolated metastases demonstrated a significant increased survival at 5 years and beyond in the range of over 30% and a surgical mortality of about 5%. Resection in such cases is no longer controversial. However, one half to two thirds of patients undergoing hepatic resection for cure have recurrence of disease, leading to a focus on factors which affect prognosis in such cases. The stage and aggressiveness of the primary, positive resection margin, positive lymph nodes, multiple lesions, short disease free interval, large size of lesion, large tumor burden, and CEA greater than 200 are negative prognostic factors. Several studies note that results seem to be better if there is a delay between resection of a primary tumor and resection of a synchronous liver metastasis.
Improvements in surgical technique and better imaging capability have led to improvement in results in cases of minimal disease, and have led some to extend the resection to multiple segments in selected patients whose general medical condition is good. The determinant of the extent of resection is the amount of functional liver tissue left. Results from complex resections have approached those of simple cases in some studies. Thermal ablation by radiofrequency probe has largely supplanted cryosurgery, and shows promise as an adjunctive modality for resectable metastasis, and as a primary modality for unresectable disease. Multimodality therapy combining chemotherapy with resection and thermal ablation, and enhanced early detection of recurrence may lead to further improvements in disease free and overall survival.
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