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 protection against metastasis. The evidence has been examined and the plausibility of such a phenomenon is reviewed.
METHODS: A systematic literature review was conducted with analysis of combined data from post-mortem 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-Haenszel (MH) fixed-effects estimate of the odds ratio was 0. 47 (95 per cent confidence interval (c.i.) 0.41-0.53; chi2 = 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; chi2 = 28, 1 d.f., P < 0.001). For tumours arising within the distribution of the portal vein, the crude rate of metastasis 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. 0.37-0.54; chi2 = 68.2, 5 d.f., P < 0.001). The DL pooled odds ratio was 0.44 (95 per cent c.i. 0.28-0.70; chi2 = 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 lower than that to normal liver. The degree of protection for tumours arising from within the distribution of the portal vein is neither greater nor less than it is overall. Eastern and Western populations appear to have a similar degree of risk reduction. The differences noted were significant on testing in the meta-analysis, but confounding bias accounting for these differences has not been excluded.