Table 1.
Characteristics of included case–control studies
| Study name (reference) | Study location | Age- standardized incidence rate per 100 000* (reference) | Recruitment period | No. of case subjects/No. of control subjects | Matching | Source of control subjects | Questionnaire administration | Blood collection, processing, and storage |
| South Africa (19) | South Africa: Johannesburg | 15 (44) | 1995–2006 | QV1†: 290/455 | Category matched; age, serum storage time, sex | Hospital, patients with cancers unrelated to smoking, alcohol, or HPV infection | Face-to-face interviews conducted by trained nurses | Collection shortly after diagnosis and before treatment (all subjects). Processed within 3–8 h at room temperature, then stored at −20°C to −35°C. |
| QV2†: 407/655 | ||||||||
| Total: 697/1110 | ||||||||
| Australia (40) | Australia: country wide | 5 (45) | 2001–2005 | 211/424 | Category matched; age, sex | Population control subjects randomly selected from the electoral roll | Self-completed mailed questionnaires | Collection within 3 mo of diagnosis (case subjects) or interview (control subjects). Processed within 2 d at room temperature and then stored at −20°C to −80°C. |
| Central and Eastern Europe (41) | Romania: Bucharest; Poland: Lodz; Russia: Moscow; Czech Republic: Olomouc, Prague | 6 (9) | 1998–2003 | 157/314 | Directly matched; age, serum storage time, sex, study center | Hospital, patients with conditions unrelated to smoking, alcohol, or HPV infection | Face-to-face interviews | Collection shortly after diagnosis and before treatment (all subjects). Processed within a few hours at room temperature and then stored at −80°C. |
| Brazil (42) | Brazil: Rio, Pelotas, Goiania | 8 (1) | 2000–2003 | 157/314 | Directly matched; age, serum storage time, sex, study center | Hospital, patients with conditions unrelated to smoking, alcohol, or HPV infection | Face-to-face interviews | Collection shortly after diagnosis and before treatment (all subjects). Processed within a few hours at room temperature and then stored at −80°C. |
| Iran (13) | Iran: Eastern Golestan Province | 40 (46) | 2003–2007 | 220/221 | Directly matched; age, sex, neighborhood | Neighborhood control subjects randomly selected from family health census | Face-to-face interviews conducted by trained nurses and physicians | Collection shortly after diagnosis and before treatment (case subjects) or at time of interview (control subjects). Processed within 1 h (case subjects) or 12 h (controls) at 4°C and then stored at −80°C. |
| China (43) | China: Shanxi Province | 50 (47) | 1998–2004 | 119/119 | Directly matched; age, sex, neighborhood | Neighborhood control subjects nominated by matched case subject | Face-to-face interviews conducted by trained nurses | Collection shortly after diagnosis and before treatment (case subjects) or attime of interview (control subjects). Processed within 1–4 d of refrigeration (case subjects) or storage in wet ice (control subjects) and then stored at −80°C. |
| Total | 1561/2502 |
*
Age-standardized incidence rates of esophageal carcinoma (standardized to the world standard population).
†
QV1 and QV2 represent questionnaire versions one and two, respectively, of the South African study. Version 2 (after 1998) elicited more detailed information on smoking and alcohol consumption than version 1. In the pooled analyses examining exposure to smoking and alcohol, multilevel smoking and alcohol covariates were used for the subset of South African participants who responded to the latter questionnaire version. In the pooled analyses examining serological marker associations, exposure to alcohol and smoking was defined as ever vs never for all South African participants.