BOSTON – Nonalcoholic fatty liver disease without cirrhosis appears to be a significant contributor to the rise in the incidence of hepatocellular carcinoma in the past two decades, according to a study linking population-based data from the National Cancer Institute with Medicare enrollment and claim files during 1993-2007.
"Our data suggest a unique underlying pathophysiology for development of HCC [hepatocellular carcinoma] in noncirrhotic NAFLD [nonalcoholic fatty liver disease]," Dr. Rubayat Rahman said at the annual meeting of the American Association for the Study of Liver Diseases.
The finding may help to explain the rise in the incidence of the malignancy, which has had no clear explanation, added Dr. Rahman of the division of gastroenterology and hepatology at the University of Missouri, Columbia.
Of 17,895 HCC cases in the linked Surveillance, Epidemiology and End Results (SEER)-Medicare database, 2,863 (16%) had only NAFLD without any other risk factors or etiologies for HCC. The linked database covers 30% of the U.S. Medicare population. SEER itself contains data from 18 cancer registries covering 28% of the U.S. population, and 93% of the individuals in the database who are at least 65 years are matched to a Medicare enrollment file.
At 16%, NAFLD was third most common risk factor for HCC after infection (44%) and alcoholic diseases (19%) – 21% were other causes – but it was the second most common risk factor after infection in Asians and Pacific islanders, said Dr. Rahman.
Cirrhosis was not present in 36% of the NAFLD-related HCC cases; of those, 18% had only steatosis and not nonalcoholic steatohepatitis (NASH) or other adverse changes in pathology. Patients without cirrhosis more often had early-stage disease (stage I or II) than did those with cirrhosis (62% vs. 44%), as well as favorable grades (I or II, 76% vs. 56%).
Although the annual percentage change of NAFLD-related HCC with cirrhosis has increased since 1993, 1999 marked a point when the annual growth of NAFLD-related cases of HCC without cirrhosis outpaced those with cirrhosis. The average number of cases per year of NAFLD-related HCC without cirrhosis grew significantly from 51 in 1993-2000 to 88 in 2001-2007, compared with no change in cases with cirrhosis.
Three components of the metabolic syndrome – body-mass index greater than 30 kg/m2, type 2 diabetes mellitus, and dyslipidemia – occurred in significantly greater proportions of patients with NAFLD-related HCC without cirrhosis than in those with cirrhosis. The odds of developing HCC for each of those three components among noncirrhotic NAFLD patients was higher than for those with cirrhotic NAFLD, although the overall odds of developing HCC were higher among patients with cirrhotic NAFLD (odds ratio, 16.5) than in those with noncirrhotic NAFLD (OR, 3.1).
One audience member expressed concern about determining the presence of cirrhosis or NASH in the data without a systematic assessment of histopathology performed in a centralized way, but Dr. Rahman noted that the Medicare-matched SEER data have CPT procedural codes and ICD-9 diagnostic codes for diagnoses made through liver biopsy. Another attendee also suggested caution in calling NAFLD a risk factor for cancer alone because the people in the database have a higher rate of cancer, and the database does not include the peak of NASH at age 55 years.
None of the study investigators had relevant financial disclosures.