AICR’s latest report on liver cancer found strong evidence that overweight and obesity increases risk of this cancer. Obesity is also a risk factor for a type of liver inflammation called non-alcoholic fatty liver disease (NAFLD).
It is already recognized that NAFLD increases the risk of liver cancer. Now a study suggests that NAFLD links to other cancers, including colorectal and breast.
The study was published this week in the Journal of Hepatology.
In the study, researchers analyzed the records of almost 26,000 Koreans who had a comprehensive health check-up including an abdominal ultrasound (to diagnose NAFLD) and were cancer-free at least one year afterwards. After an average of 7.5 years, a third of the individuals were diagnosed with NAFLD. The study found that cancer incidence among this group was 32 percent higher than those without NAFLD.
When adjusting for age, diabetes, cholesterol and other metabolic factors, three cancers stood out as having a link with NAFLD. Liver cancer had the strongest association by far: those with NAFLD were about 16 times more likely to develop liver cancer compared to those without NAFLD. The men in this NAFLD group were also twice as likely to develop colorectal cancer and the women almost twice as likely to develop breast cancer. These estimates were based on relatively small numbers: 14 cases of liver cancers, 76 cases of colorectal cancer, and 91 cases of breast cancer.
With obesity linking to post-menopausal breast cancer, the researchers conducted another analysis that classified the women as obese or non-obese according to their BMI. In this analysis, there were no significant associations between NAFLD and breast cancer among the obese individuals.
The strong relationship between NAFLD and liver cancer can be considered causal, but not necessarily for the other two cancers, according to an accompanying editorial. There are questions whether NAFLD caused cancer development or if cancer development was a result of the metabolic syndrome. Colorectal cancer is related to type 2 diabetes and obesity, for example, which link to the metabolic syndrome.
Limitations of the study include that it was observational, and had a relatively small number of cancer cases within the period of the study. This study also was conducted among a specific group of Korean individuals and the findings may not apply to different populations. More research is needed.
NAFLD is one of the most common causes of liver diseases in the United States with 30 to 40 percent of adults having NAFLD, according to the National Institutes of Health. Studies suggest NAFLD is also increasing around the world.
Along with obesity, AICR has found strong evidence that having three or more alcoholic drinks regularly increases the risk of liver cancer; coffee lowers risk. More research on reducing risk of liver cancer is available here.
The authors write they have nothing to disclose regarding funding.
Gi-Ae Kim et al. Association between nonalcoholic fatty liver disease and cancer incidence rate, Journal of Hepatology. Published online: November 14, 2017.
NAFLD and cancer: More cause for concern? Journal of Hepatology. Published online: October 20, 2017.
National Institute of Diabetes and Digestive and Kidney Diseases. Definition & Facts of NAFLD & NASH.
New Studies Highlight Increasing Global Prevalence of NAFLD/NASH and Its Considerable Toll. Medscapre. January 2017.
AICR/WCRF. Diet, Nutrition, Physical Activity and Liver Cancer. 2015.