Each additional cup of coffee per day resulted in a 20% risk reduction (RR, 0.80; 95% CI: 0.77-0.84). This split into a 23% risk reduction in the case-control studies (RR, 0.77; 95% CI: 0.71-0.83) and a 17% risk reduction in the cohort studies (RR, 0.83; 95% CI: 0.78-0.88). A temporal analysis of risk reduction for any coffee consumption showed an increase from 20% risk reduction in 2000 (RR, 0.8; 95% CI: 0.50-1.29) to 41% in 2007 (RR, 0.59; 95% CI: 0.48-0.72), which has remained stable at about 40% the past several years.
Accounting for the most [significant] risk factors for liver cancer had little effect on the risk ratios. These factors included hepatitis B and C infections, cirrhosis, and other liver diseases, socioeconomic status, alcohol consumption, and smoking.
Dr. Bravi’s team suggested that the risk reduction effect could be a real, causal effect arising from antioxidants and other minerals in coffee that may inhibit liver carcinogenesis or from the inverse association between coffee and cirrhosis or coffee and diabetes, both conditions known risk factors for liver cancer. Or, the effect could result, at least in part, from reduced consumption of coffee among patients with cirrhosis or other liver disease.
"Thus, a reduction of coffee consumption in unhealthy subjects cannot be ruled out, although the inverse relation between coffee and liver cancer also was present in subjects with no history of hepatitis/liver disease," the researchers wrote. Yet, they also noted the potentially limited utility of coffee risk reduction given the greater impact on reducing liver cancer risk from hepatitis B vaccination, prevention of hepatitis C, and reduction of alcoholic drinking.
The pancreatic cancer study was funded by the European Commission and the International Agency for Research on Cancer, with a long list of additional societies, foundations, and educational institutions supporting the individual national cohorts. The hepatocellular carcinoma study was funded by a grant from the Associazione Italiana per la Ricerca sul Cancro. The authors in both studies reported no disclosures.