Evidence that metastasis is less common in cirrhotic than normal liver: a systematic review of post-mortem case-control studies

Background: It has been hypothesized that the cirrhotic liver is afforded p rotection against metastasis. The evidence has been examined and the plausi bility of such a phenomenon is reviewed. Methods: A systematic literature review was conducted with analysis of comb ined data from postmortem case-control studies. Results: Overall, the crude rate of metastasis to normal liver was 37.3 per cent, while the rate to cirrhotic liver was 23.7 per cent. The Mantel-Haen szel (MH) fixed-effects estimate of the odds ratio was 0.47 (95 per cent co nfidence interval (c.i.) 0.41-0.53; chi(2) = 136, 11 d.f., P < 0.001). The DerSimonian-Laird (DL) random-effects estimation of the odds ratio was 0.42 (95 per cent c.i. 0.31-0.58; chi(2) = 28, 1 d.f, P < 0.001). For tumours a rising within the distribution of the portal vein, the crude rate of metast asis to normal liver was 47.6 per cent, whereas the rate to cirrhotic liver was 29.8 per cent. The MH estimate of the odds ratio was 0.45 (95 per cent c.i. 0.37-0.51; chi(2) = 68.2, 5 d.f., P < 0.001). The DL pooled odds rati o was 0.44 (95 per cent c.i. 0.28-0.70; chi(2) = 12.3, 1 d.f., P < 0.001). The MH and DL pooled estimates of the odds ratio were similar for groups of patients from the East (Japan) and the West (Europe and the USA). Conclusion: The post-mortem evidence reviewed suggests that the likelihood of metastasis to the cirrhotic liver is lon er than that to normal liver. T he degree of protection for tumours arising from within the distribution of the portal vein is neither greater nor less than it is overall. Eastern an d Western populations appear to have a similar degree of risk reduction. Th e differences noted were significant on testing in the meta-analysis, but c onfounding bias accounting for these differences has not been excluded.