Supplementary Material for: Investigation of novel urinary biomarkers in hepatocellular carcinoma risk in a predominantly African American population.

Introduction
African Americans are at increased risk of hepatocellular carcinoma (HCC) compared to other racial and ethnic groups. We investigated the associations of four urinary biomarkers of prostaglandin E2(PGE-M), prostacyclin (PGI-M), and thromboxane (11dTxB2) synthesis and the ratio of PGI-M to 11dTXB2 with HCC risk in a cohort of predominantly African American population.

Methods
We conducted a nested case-control study (50 cases; 43 with HCC, 151 controls) in the Southern Community Cohort Study (SCCS), a large prospective cohort study including over 80,000 study participants of whom two-thirds are African Americans. Urine samples were collected at enrollment and subsequently analyzed to assess biomarker levels. Multivariable regression models adjusted for age, race, sex, BMI, smoking status, NSAID use, education level, income and alcohol consumption were used to assess the relationship between the biomarker and HCC risk.

Results
Only 11dTxB2 (OR=11.50; 95%CI [2.34-56.47] for highest tertile vs lowest tertile, p=0.004) and the PGI-M/11dTXB2 ratio of the second quartile (0.25-0.49) (OR=5.16; 95%CI[1.44-18.47];p=0.01) were significantly associated with increased risk of liver cancer.

Conclusion
11dTXB2 and PGI-M/11dTXB2 ratio may be urinary markers of HCC risk, particularly among African Americans and future prospective studies are needed to evaluate this finding further and to develop accessible methods.