Risk factors associated with nasopharyngeal carcinoma.

We performed a case-control study of nasopharyngeal squamous-cell carcinoma to identify risk factors associated with the disease. Interviews with 156 patients and 267 controls revealed that increased risk was significantly associated with a prior history of ear, nose or throat disease (relative risk = 1.8, P = 0.006) and occupational exposure to fumes (relative risk = 2.0, P = 0.006), smoke (relative risk = 3.0, P = 0.008) and chemicals (relative risk = 2.4, P = 0.006). Among Chinese, other Asians and Mexican-Americans, increased risk was also associated with foreign birthplace (relative risk = 2.1, P = 0.04), probably reflecting childhood exposure to carcinogens in inhaled smoke. In Chinese patients the risk associated with foreign birthplace and occupational exposure increased among those with HLA-A2 and less than two antigens at the B locus, suggesting a genetic variation in susceptibility.