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Tobacco smoking is a major risk factor for head and neck cancer (HNC). Family history of cancer is also associated with HNC. This association lies in the difficulty in balancing the influence of hereditary vs shared environmental factors. We aimed to assess the role of smoking status of affected relatives on the risk of HNC. This study comprised 567 patients with HNC and 328 controls without cancer admitted in five centers in Sao Paulo State, Brazil, from 2005 to 2009; all of them had at least one parent or sibling with cancer of any site reported. Multivariate unconditional logistic regression was used to assess the effect of tobacco smoking in affected relatives on the risk of HNC. ORs were adjusted on socioeconomic status, tobacco smoking, alcohol drinking, age, sex and the number of relatives that experienced cancer. Having one or more smoker affected relative was associated with a higher risk of HNC (OR=2.39; 95% CI 1.69 to 3.37). This association remained high when stratification by cancer subsites was performed: oral cavity (2.11; 1.41 to 3.17), oropharynx (2.84; 1.54 to 5.23), larynx (4.05; 2.36 to 6.93). In conclusion, cancer affected relatives of HNC cases are more exposed to tobacco smoking than cancer affected relatives of controls. This finding suggests that lifestyle factors of parents or siblings with cancer history may play a role on the association between family history of cancer and HNC.

Background The potential contribution of denture-related sores to oral carcinogenesis still fuels controversies. This study assessed the association between recurrent denture-related sores and squamous cell carcinoma in anatomic sites of the mouth that are specifically at risk of sores by ill-fitting dentures. Methods We conducted a hospital-based case-control study comprising 71 histologically-confirmed cases of squamous cell carcinoma in anatomic sites of the mouth that were specifically at risk of developing sores due to ill-fitting dentures, who were attended at two hospitals in Sao Paulo, Brazil; and 240 controls without cancer, recruited from outpatient units of the same hospitals. Associations were assessed by multivariate logistic regression conditioned on socio-demographic (family income) and behavioural characteristics (tobacco smoking, alcohol drinking and dietary patterns). Results The association between ill-fitting dentures and mouth cancer was statistically significant in the multivariate model, which adjustment for socio-demographic and behavioural characteristics: OR=3.98 (95% CI 1.06 to 14.96). The specific assessment of association between tumours in the lower jaw and sores by mandibular dentures confirmed this result (OR=6.39; 95% CI 1.49 to 29.52). Conclusions These results reinforce the hypothesis that an appropriate application and monitoring of dental prosthesis represent a non-negligible scope for cancer prevention.