Familial risk in oral and pharyngeal cancer

We examined the relationship between a family history of cancer and risk of roal and pharyngeal cancer using epidemiological data from a large case-control investigation of these tumours. 487 (45.7%) of the cases and 485 (41.0%) of the controls reported cancer in a parent or a sibling. After controlling for age, race, sex, study location, respondent status and smoking and alcohol use, the OR associated with any cancer in the family was 1.1 [95% confidence interval (CI) 0.9-1.3]. Risks were non-significantly elevated among those with a history of cancers arising from the oral cavity/pharynx (OR = 1.2, 95% CI 0.7-2.3), oesophagus/larynx (OR = 1.6, 95% CI 0.7-3.8) and lung (OR = 1.2, 95% CI 0.8-1.8), with the excess risk primarily among those for whom a male relative, particularly a brother, was affected with these smoking-related cancers. In addition, an elevated risk of oral/pharynx cancer was found among those whose sisters developed other cancers (OR = 1.6, 95% CI 1.1-2.2). Subsite analyses revealed stronger elevated risks of smoking-related cancers in relatives of pharyngeal cancer cases (OR = 1.7, 95% CI 1.1-2.8) than of oral cancer patients. The data indicate that there is at most a weak familial aggregation of oral/pharynx cancers. Furthermore, since the excess familial risk of oral/pharynx cancer was associated with smoking-related cancers among male but not female relatives, it seems likely that environmental factors (notably smoking and drinking) contribute to the familial tendency observed in this study. The results underscore the need to collect risk profile information on relatives in future studies to disentangle genetic from environmental determinants.