Adenocarcinomas of the upper gastrointestinal tract (UGI) show remarkable male predominance. As smoking is a well-established risk factor, we investigated the role of tobacco smoking in the male predominance of UGI adenocarcinomas in the United States NIH-AARP Diet and Health study.
A questionnaire was completed by 281,422 men and 186,133 women in 1995-1996 who were followed until Dec 31, 2003. Incident UGI adenocarcinomas were identified by linkage to state cancer registries. We present age-standardised cancer incidence rates per 100,000 person-years and Male/Female ratios (M/F) calculated from age-adjusted Cox proportional hazards models, both with 95% confidence intervals.
After 2,013,142 person-years follow up, 338 adenocarcinomas of the oesophagus, 261 of gastric cardia, and 222 of gastric non-cardia occurred in men. In women, 23 tumours of oesophagus, 36 of gastric cardia, and 88 of gastric non-cardia occurred in 1,351,958 person-years follow up. The age-standardised incidence rate of all adenocarcinoma sites were 40.5 (37.8-43.3) and 11.0 (9.2-12.8) in men and women. Among smokers, the M/F of all UGI adenocarcinomas was 3.4 (2.7-4.1), with a M/F of 7.3 (4.6-11.7) for tumours in oesophagus, 3.7 (2.5-5.4) for gastric-cardia, and 1.7 (1.2-2.3) for gastric non-cardia. In non-smokers, M/F ratios were 14.2 (5.1-39.5) for oesophagus, 6.1 (2.6-14.7) for gastric cardia, 1.3 (0.8-2.0) for gastric non-cardia. The overall M/F ratio was 3.0 (2.2-4.3).
the male predominance was similar in smokers and non-smokers for these cancer sites. These results suggest that the male predominance of upper GI adenocarcinomas cannot be explained by differences in smoking histories.