Metabolic disorders and the risk of nasopharyngeal carcinoma: a case-control study in Italy.

The aim of this study is to evaluate the association between metabolic disorders and the risk of nasopharyngeal carcinoma, considering different histological subtypes. Between 1992 and 2008, we carried out a multicentre case-control study in Italy. One-hundred and ninety-seven White patients with histologically confirmed nasopharyngeal carcinoma were enrolled as cases. The control group included 592 cancer-free patients, frequency matched by study centre, area of residence, sex, age and period of interview. Odds ratios (OR) and corresponding 95% confidence intervals (CI), for nasopharyngeal carcinoma according to obesity and self-reported history of other metabolic disorders, were calculated through logistic regression models adjusted for matching variables and tobacco smoking and drinking habits. Obesity (OR=1.44; 95% CI: 0.88-2.36), diabetes mellitus (OR=0.91; 95% CI: 0.42-1.98), hypertension (OR=0.79; 95% CI: 0.48-1.32), hypercholesterolaemia (OR=1.41; 95% CI: 0.84-2.35) and metabolic syndrome (i.e. at least three among the four previously cited metabolic disorders; OR=1.11; 95% CI: 0.86-1.43) were not significantly associated with the overall risk of nasopharyngeal carcinoma. However, the associations observed for diabetes mellitus, hypercholesterolaemia and metabolic syndrome were stronger among differentiated nasopharyngeal carcinomas than among undifferentiated ones. In particular, 21.7% of differentiated nasopharyngeal carcinoma cases and 7.8% of controls reported a history of metabolic syndrome (OR=3.37; 95% CI: 1.05-10.81). The results of the study indicated no overall association between metabolic disorders and nasopharyngeal carcinoma. Nonetheless, although the small sample size calls for caution in interpretation, metabolic disorders could increase the risk of differentiated nasopharyngeal carcinoma. This finding further supports a different aetiology of the two histological subtypes.