Surgical Treatment of Colorectal
Metastases to the Liver
Colorectal cancer develops in more than 138,000 patients and is responsible for more than 55,000 deaths in the United States every year.1 Up to one fourth of patients diagnosed with colorectal cancer present with liver metastases. In addition, liver metastases are detected in many more patients after diagnosis, such that by the time of death up to 70 percent of patients with colorectal cancer have metastatic disease to the liver.
Since the first systematic attempts to treat liver metastasis from colorectal cancer by surgical excision three decades ago,4this aggressive approach has gained general acceptance. A large number of studies have demonstrated that resectional therapy of colorectal liver metastasis is not only safe, but also potentially curative. The rationale for the surgical approach was based on two important assumptions that have been verified by data. First, isolated liver metastasis to the liver can occur without tumor growth elsewhere, and second, surgical removal of liver tumors can be performed with low morbidity and mortality.
This summary starts with a review of the natural history of colorectal liver metastases and results of systemic chemotherapy as treatment in this clinical setting. A review of surgical results follows, starting with surgical resection and concluding with alternative surgical options that are available. It is clear that at present surgical excision is the standard therapy for resectable liver metastases from colorectal primaries.
Colorectal cancer metastatic to the liver was long presumed incurable, and data from studies during the late 1960s to the early 1980s provide a glimpse of the natural history of colorectal metastasis to the liver (Table 1). Certain conclusions are clear from these data. First, colorectal metastasis to the liver is common. As many as 25 percent of patients presenting with colorectal primaries will be found to have synchronous liver metastasis.2In addition, after treatment of the primary as many as 50 percent of patients will recur with metachronous liver metastasis. Given the estimate of 138,000 new cases of colorectal cancer each year in the United States, at least 46,000 of these patients will present for evaluation of liver metastases during the course of the disease. Second, survival for untreated colorectal metastases to the liver can be measured in months, and five-year survival after discovery of such disease is less than two percent.
Many of the natural history studies have been criticized for lack of data on extent of liver involvement. In two of the series presented, the authors attempted to distinguish potentially resectable from unresectable disease. In the study from Wood et al at the Glasgow Royal Infirmary, of the 113 patients reported were thought retrospectively to have potentially resectable disease. In this group the one-year survival for untreated but resectable disease was 46 percent (compared with six percent for the unresectable cohort); three-year survival was 12 percent (compared with zero percent) and five-year survival was three percent.14 In the study from Wagner et al, the three year survival for untreated resectable disease was 14 percent (compared with four percent for unresectable disease) and two percent at five years (compared with two percent). From these data, it appears that although solitary lesions or unilobar disease appear to have better prognosis, the five-year survival was still consistently less than three percent. Liver metastasis from colorectal cancer is therefore common and has a uniformly poor outcome when untreated.
Many systemic chemotherapeutic regimens have been tested for metastatic colorectal cancer. The most consistently active agent for this disease has been 5fluorouracil (5-FU), and most regimens have been based on this agent (Table 2). Few studies, and certainly none of the most recent studies, have specifically examined the role of systemic chemotherapy for resectable liver disease. However, it is clear that for most chemotherapeutic regimens, less than one third of patients with liver metastases have shown any response. It is unfortunate that the most recent trials for what is currently the standard chemotherapeutic regimen, namely 5-FU and leucovorin, do not indicate the percentage of patients with isolated liver tumors that respond to this regimen. Given that the overall response to these regimens is 26 to 44 percent, it is unlikely that liver-specific responses are significantly greater than this.
Given the poor outcome of unresected metastatic colorectal cancer to the liver, it is understandable that an increasingly aggressive surgical approach has been undertaken in the last two decades for treatment of this disease. This aggressive resectional approach coincided and partly produced improvements in the understanding of liver anatomy, in surgical techniques, and in anesthetic support for liver resection. The result is overwhelming evidence that not only is surgical resection a safe option, it is also a rational and potentially curative treatment for hepatic metastatic disease from colorectal tumors.
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