Liver Resection Improves Survival in Colorectal Cancer Patients : Causal-effects From Population-level Instrumental Variable Analysis

Resection of colorectal liver metastases (CLM) in selected patients has evolved as the standard of care during the last 20 years. In the absence of prospective randomized clinical trials, a survival benefit has been deduced relative to historical controls based on actuarial data. There is now sufficient follow-up on a significant number of patients to address the curative intent of resecting CLM. Retrospective review of a prospectively maintained database was performed on patients who underwent resection of CLM from 1985 to 1994. Postoperative deaths were excluded. Disease-specific survival (DSS) was calculated from the time of hepatectomy using the Kaplan-Meier method. There were 612 consecutive patients identified with 10-year follow-up. Median DSS was 44 months. There were 102 actual 10-year survivors. Ninety-nine (97%) of the 102 were disease free at last follow-up. Only one patient experienced a disease-specific death after 10 years of survival. In contrast, 34% of the 5-year survivors suffered a cancer-related death. Previously identified poor prognostic factors found among the 102 actual 10-year survivors included 7% synchronous disease, 36% disease-free interval less than 12 months, 25% bilobar metastases, 50% node-positive primary, 39% more than one metastasis, and 35% tumor size more than 5 cm. Patients who survive 10 years appear to be cured of their disease, whereas approximately one third of actual 5-year survivors succumb to a cancer-related death. In well-selected patients, there is at least a one in six chance of cure after hepatectomy for CLM. The presence of poor prognostic factors does not preclude the possibility of long-term survival and cure.

To examine trends in outcomes of patients undergoing resection at a single tertiary care referral center over a 16-year period. Hepatic resection is considered the treatment of choice in selected patients with colorectal metastasis confined to the liver. Although a variety of retrospective studies have demonstrated improvements in short-term outcomes in recent years, changes in long-term survival over time are less well-established. Data from 226 consecutive patients undergoing potentially curative liver resection for colorectal metastases between 1984 and 1999 were analyzed. Actuarial survival rates related to prognostic determinants were analyzed using the log-rank test. The median survival for the entire cohort was 46 months, with 5- and 10-year survival rates of 40% and 26% respectively. Ninety-three patients operated on between 1984 and 1992 were found to have an overall survival of 31% at 5 years, compared to 58% for the 133 patients operated on during the more recent period (1993-1999). Both overall and disease-free survival were significantly better in the recent time period compared with the earlier period on both univariate and multivariate analyses. Other independent factors associated with improved survival included number of metastatic tumors < or = 3, negative resection margin, and CEA < 100. Comparisons were made between time periods for a variety of patient, tumor and treatment-related factors. Among all parameters studied, only resection type (anatomical versus nonanatomical), use of intraoperative ultrasonography, and perioperative chemotherapy administration differed between the early and recent time periods. Long-term survival following liver resection for colorectal metastases has improved significantly in recent years at our institution. Although the reasons for this survival trend are not clear, contributing factors may include the use of newer preoperative and intraoperative imaging, increased use of chemotherapy, and salvage surgical therapy.