Table A1.

Definitions of Variables and Cut Points

Variable	Definitions and Cut Points
Sex	Male and female
Age	18-44, 45-54, 55-64, 65-74, and ≥ 75 years
Race/ethnicity	White, African American, Asian/Pacific Islander, Hispanic (identified as having Spanish/Hispanic surname or of Spanish origin regardless of the category of race/ethnicity), and Native American
Histology	Adenocarcinoma, squamous cell carcinoma, and other (other histology or not specified)
Tumor primary site	Lower third (C152, C155), middle third (C151, C154), upper third (C150, C153), and overlapping or not specified (C158, C159)
Tumor grade/differentiation	Well differentiated (grade 1), moderately differentiated (grade 2), poorly differentiated or undifferentiated (grade 3 or 4), and not determined
Treatment	Esophagectomy (partial or total esophagectomy) and radiation therapy (beam radiation or radiation; method or source not specified). Detailed information on surgery of the primary site was not available prior to 1983. Records on chemotherapy were not available in the SEER database.
Radiation sequence	No radiation/surgery, neoadjuvant radiation, adjuvant radiation, and intraoperative radiation or unknown
Marital status at diagnosis	Not married (including never married, separated, divorced, widowed, and unknown) and married (including common law)
Stage	Metastatic (SEER historic stage A code 4) and locoregional (localized or regional corresponding to SEER historic stage A code 1 or 2).
SEER registry	17 SEER registry sites (http://seer.cancer.gov/registries/list.html)
Year of diagnosis	Three intervals: 1973-1982, 1983-1995, and 1996-2007