To estimate the independent and joint effects of tobacco smoking and alcohol drinking, we analyzed data from a series of 5 hospital-based case-control studies of squamous-cell carcinoma of the esophagus conducted in high-risk areas in South America. A total of 830 case subjects and 1779 control subjects were included in the pooled analysis. All exposure characteristics of amount, duration, cessation and type of alcohol and tobacco consumed were strongly related to esophageal-cancer risk in both sexes. Women had the same exposure profile as men, but the magnitudes of the associations were lower than were those among men. Black-tobacco smoking was associated with a 2-fold increased risk as compared with the smoking of blond or mixed tobacco. Quitting either of the 2 habits significantly reduced esophageal-cancer risk. Alcohol and tobacco alone were strongly related to the risk of esophageal cancer, even in the absence of the other exposure. A history of simultaneous exposure to cigarette smoking and alcohol drinking had a strong multiplicative effect on risk. Concomitant exposure to heavy alcohol drinking and black-tobacco smoking identified the group with the highest risk for developing esophageal cancer (odds ratio = 107). A synergistic interaction was found between the 2 habits, particularly in women and in moderately exposed men. Moderate cigarette smoking without drinking and moderate alcohol drinking without smoking had a negligible effect on esophageal-cancer risk. However, simultaneous exposure to the same moderate amounts increased the risk 12- to 19-fold in men and in women respectively. The overall public-health implications of these findings are obvious for a tumor that depends on preventive strategies for its control.
Copyright 1999 Wiley-Liss, Inc.