Natural history collections provide an immense record of biodiversity on Earth. These repositories have traditionally been used to address fundamental questions in biogeography, systematics, and conservation. However, they also hold the potential for studying evolution directly. While some of the best direct observations of evolution have come from long-term field studies or from experimental studies in the lab, natural history collections are providing new insights into evolutionary change in natural populations. By comparing phenotypic and genotypic changes in populations through time, natural history collections provide a window into evolutionary processes. Recent studies utilizing this approach have revealed some dramatic instances of phenotypic change over short time scales in response to presumably strong selective pressures. In some instances evolutionary change can be paired with environmental change, providing a context for potential selective forces. Moreover, in a few cases, the genetic basis of phenotypic change is well understood, allowing for insight into adaptive change at multiple levels. These kinds of studies open the door to a wide range of previously intractable questions by enabling the study of evolution through time, analogous to experimental studies in the laboratory, but amenable to a diversity of species over longer timescales in natural populations.

ObjectiveTo analyze the cost-effectiveness of resection for liver metastases compared with standard nonsurgical cytotoxic treatment. Summary Background DataThe efficacy of hepatic resection for metastases from colorectal cancer has been debated, despite reported 5-year survival rates of 20% to 40%. Resection is confined to specialized centers and is not widely available, perhaps because of lack of appropriate expertise, resources, or awareness of its efficacy. The cost-effectiveness of resection is important from the perspective of managed care in the United States and for the commissioning of health services in the United Kingdom. MethodsA simple decision-based model was developed to evaluate the marginal costs and health benefits of hepatic resection. Estimates of resectability for liver metastases were taken from UK-reported case series data. The results of 100 hepatic resections conducted in Sheffield from 1997 to 1999 were used for the cost calculation of liver resection. Survival data from published series of resections were compiled to estimate the incremental cost per life-year gained (LYG) because of the short period of follow-up in the Sheffield series. ResultsHepatic resection for colorectal liver metastases provides an estimated marginal benefit of 1.6 life-years (undiscounted) at a marginal cost of £6,742. If 17% of patients have only palliative resections, the overall cost per LYG is approximately £5,236 (£5,985 with discounted benefits). If potential benefits are extended to include 20-year survival rates, these figures fall to approximately £1,821 (£2,793 with discounted benefits). Further univariate sensitivity analysis of key model parameters showed the cost per LYG to be consistently less than £15,000. ConclusionIn this model, hepatic resection appears highly cost-effective compared with nonsurgical treatments for colorectal-related liver metastases.Colorectal cancer is the second most common cancer in the United Kingdom, with an annual incidence steadily reported at approximately 57 per 100,000 population. 1-4Prevalence increases with age (almost 50% of cases occur in patients older than 60 4 ) and is greater in men (approximately 60% of cases). Approximately 25% of patients with colorectal cancer have detectable liver metastases at presentation (synchronous metastases). A further 25% develop metastases during the course of their disease (metachronous metastases), usually within 2 years after initial surgical treatment of their primary tumor.5 Metastatic disease of the liver remains a major cause of cancer-related death.4 Overall survival is closely related to tumor burden: patients with single or multiple metastases restricted to one lobe of the liver (unilobar disease) have an expected median survival of less than 24 months, 6 and patients with bilobar disease have a median survival of less than 18 months. 7 If untreated, most patients would not be expected to survive much beyond 9 to 12 months. 8 Conventional treatments for colorectal liver metastases are based on systemic chemotherapy, ge...