While surgical resection of colorectal liver metastases has gained widespread acceptance, the role of hepatic resection for noncolorectal liver metastases is less clear. Until recently, there were no large series to guide clinical decision making. However, the reduction in operative morbidity and mortality with major hepatic resections has allowed for a reexamination of the role of surgery in the treatment of noncolorectal liver metastases.
Over the past 2 decades, resection of liver metastases from carcinoid tumors has become part of the standard of care for patients with malignant carcinoid syndrome. This is because of the indolent nature of these tumors, which are often slow-growing. In 1961, Moertel et al defined the natural history of carcinoid tumors metastatic to the liver. The mean survival from the onset of symptoms was 8.1 years in a series of 28 patients with malignant carcinoid syndrome. Today, survival may be extended even further with the combination of resection, hormonal therapy with somatostatin analogues (octreotide), and hepatic artery embolization.
Soreide et al (1992) reported a retrospective review of 75 patients who underwent aggressive surgical management of their advanced abdominal carcinoid tumors. Of these patients, 36 underwent 1 or more interventions directed at metastatic disease in the liver: resection, hepatic artery ligation, or embolization. The median survival in this group was 216 months, compared with 48 months for patients who did not undergo hepatic intervention (P < .001). Que et al (1995) from the Mayo Clinic reviewed 75 patients, most of whom underwent hepatic resection for symptomatic metastatic neuroendocrine tumors. Fifty (75%) of these tumors were carcinoids. Resections included 38 formal lobectomies or extended resections and 38 nonanatomic resections. Perioperative mortality was 2.4% and morbidity was 24%. The 4-year survival rate was 73%, but perhaps more important, symptomatic response was achieved in 90% of patients, with a mean duration of response of 19.3 months.
Chen et al (1998) reported on a series of 38 patients with liver-only metastases from neuroendocrine tumors. Most tumors (21) were metastatic carcinoid tumors. The 5-year actuarial survival rate was 73% for the 15 patients who were able to undergo complete resection of their disease. This was significantly better than the 29% 5-year actuarial survival rate observed for the 23 patients who had a similar tumor burden but were believed to have unresectable disease. Although not randomized, this small series suggests that hepatic resection may not only provide palliation in these highly symptomatic patients but also improve survival in selected patients.
Finally, orthotopic liver transplantation has been suggested as an alternative therapy for selected patients with neuroendocrine hepatic metastases. Le Treut et al (1997) reported a 4-year survival rate of 69% in a series of 15 patients who underwent orthotopic liver transplantation for metastatic carcinoid tumors. This is in contrast to a 4-year survival rate of 8% reported for 16 patients with noncarcinoid apudomas. Of note, however, were a 19% mortality rate and a 48% incidence of major surgical complications. Further long-term studies are needed to clarify the role of transplantation in the treatment of hepatic metastases from neuroendocrine tumors. Given the scarcity of organ donors and limited resources, it is unlikely that organ transplantation will be available to many patients with metastatic carcinoid tumors in the near future.
The role of hepatic resection for metastases from nonneuroendocrine primary tumors is less well defined. Recently, several institutions have published their experience with noncolorectal, nonneuroendocrine metastases, and this provides some guidelines for selecting patients who will benefit from hepatic resection. The review of patients who underwent surgery at M. D. Anderson indicated a 5-year actuarial survival rate of 44%, with a median survival of 54 months, for 45 patients undergoing resection of noncolorectal liver metastases (Tuttle, 1998). Similarly, Harrison et al (1997) reported a 5-year overall survival rate of 37% for 96 patients undergoing liver resection for noncolorectal, nonneuroendocrine metastases. More than 78% of the primary tumors in this series were genitourinary or soft-tissue tumors. By multivariate analysis, the only predictors of increased survival were a disease-free interval of less than 36 months prior to discovery of liver metastases; curative resection; and primary tumor type (genitourinary > soft tissue > gastrointestinal). These results confirm the findings of Schwartz (1995), who found by a review of the literature that long-term survival was possible for patients with liver metastases from renal tumors (particularly Wilms' tumor) but not for those with soft-tissue or gastrointestinal (noncolorectal, nonneuroendocrine) primary tumors.
Thus, despite the fact that recent survival data for patients undergoing resection of noncolorectal, nonneuroendocrine metastases are encouraging, in most patients disease will eventually recur. Patient selection is critical when opting for resection, and resection should be considered only in the context of a multimodality treatment plan at specialized centers.
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