TABLE 1.

Variable Definitions and Categories

Variable	Definitions and Categories
Sex	Male and female
Age, y	18–44, 45–54, 55–64, 65–74, and ≥75
Race/ethnicity	White, African American, Asian/Pacific Islander, Hispanic (identified as having Spanish/Hispanic surname or of Spanish origin regardless the category in race/ethnicity), and Native American
Marital status at diagnosis	Not married (including never married, separated, divorced, widowed, and unknown) and married (including common-law marriage)
Birthplace	US-born, abroad low-incidence region, abroad high-incidence region, and unknown
Tumor stage	Single lesion in 1 lobe, multiple tumors, vascular invasion, and metastatic disease
Tumor size, cm	<3, 3 to <5 cm, ≥5 cm, and unknown
AJCC tumor grade/differentiation	Well differentiated (grade 1), moderately differentiated (grade 2), poorly differentiated or undifferentiated (grade 3 or 4), and not determined
Initial surgical procedure	None or unknown, local therapy (photodynamic therapy, electrocautery, fulguration, cryosurgery, laser, percutaneous ethanol injection, heat-radiofrequency ablation, or other), resection (wedge or segmental resection, lobectomy, or hepatectomy), and liver transplantation
Initial radiation	No, yes, and unknown
Year of diagnosis	4 periods: 1988 to 1997, 1998 to 2002, 2003 to 2005, and 2006 to 2010
SEER registry	18 SEER registry sites (seer.cancer.gov/registries/list.html)

Abbreviation: SEER, Surveillance, Epidemiology, and End Results.