Background: The magnitude of risk conferred by the interaction between tobacco and alcohol use on the risk of head and neck cancers is not clear because studies have used various methods to quantify the excess head and neck cancer burden. Methods: We analyzed individual-level pooled data from 17 European and American case-control studies (11,221 cases and 16,168 controls) participating in the International Head and Neck Cancer Epidemiology consortium. We estimated the multiplicative interaction parameter (ψ) and population attributable risks (PAR). Results: A greater than multiplicative joint effect between ever tobacco and alcohol use was observed for head and neck cancer risk (ψ = 2.15; 95% confidence interval, 1.53-3.04). The PAR for tobacco or alcohol was 72% (95% confidence interval, 61-79%) for head and neck cancer, of which 4% was due to alcohol alone, 33% was due to tobacco alone, and 35% was due to tobacco and alcohol combined. The total PAR differed by subsite (64% for oral cavity cancer, 72% for pharyngeal cancer, 89% for laryngeal cancer), by sex (74% for men, 57% for women), by age (33% for cases 60 years), and by region (84% in Europe, 51% in North America, 83% in Latin America). Conclusions: Our results confirm that the joint effect between tobacco and alcohol use is greater than multiplicative on head and neck cancer risk. However, a substantial proportion of head and neck cancers cannot be attributed to tobacco or alcohol use, particularly for oral cavity cancer and for head and neck cancer among women and among young-onset cases. (Cancer Epidemiol Biomarkers Prev 2009;18(2):541–50)

At least 75% of head and neck cancers are attributable to a combination of cigarette smoking and alcohol drinking. A precise understanding of the independent association of each of these factors in the absence of the other with the risk of head and neck cancer is needed to elucidate mechanisms of head and neck carcinogenesis and to assess the efficacy of interventions aimed at controlling either risk factor. We examined the extent to which head and neck cancer is associated with cigarette smoking among never drinkers and with alcohol drinking among never users of tobacco. We pooled individual-level data from 15 case–control studies that included 10244 head and neck cancer case subjects and 15227 control subjects, of whom 1072 case subjects and 5775 control subjects were never users of tobacco and 1598 case subjects and 4051 control subjects were never drinkers of alcohol. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression models. All statistical tests were two-sided. Among never drinkers, cigarette smoking was associated with an increased risk of head and neck cancer (OR for ever versus never smoking = 2.13, 95% CI = 1.52 to 2.98), and there were clear dose–response relationships for the frequency, duration, and number of pack-years of cigarette smoking. Approximately 24% (95% CI = 16% to 31%) of head and neck cancer cases among nondrinkers in this study would have been prevented if these individuals had not smoked cigarettes. Among never users of tobacco, alcohol consumption was associated with an increased risk of head and neck cancer only when alcohol was consumed at high frequency (OR for three or more drinks per day versus never drinking = 2.04, 95% CI = 1.29 to 3.21). The association with high-frequency alcohol intake was limited to cancers of the oropharynx/hypopharynx and larynx. Our results represent the most precise estimates available of the independent association of each of the two main risk factors of head and neck cancer, and they exemplify the strengths of large-scale consortia in cancer epidemiology.

It is uncertain whether male circumcision reduces the risks of penile human papillomavirus (HPV) infection in the man and of cervical cancer in his female partner. We pooled data on 1913 couples enrolled in one of seven case–control studies of cervical carcinoma in situ and cervical cancer in five countries. Circumcision status was self-reported, and the accuracy of the data was confirmed by physical examination at three study sites. The presence or absence of penile HPV DNA was assessed by a polymerase-chain-reaction assay in 1520 men and yielded a valid result in the case of 1139 men (74.9 percent). Penile HPV was detected in 166 of the 847 uncircumcised men (19.6 percent) and in 16 of the 292 circumcised men (5.5 percent). After adjustment for age at first intercourse, lifetime number of sexual partners, and other potential confounders, circumcised men were less likely than uncircumcised men to have HPV infection (odds ratio, 0.37; 95 percent confidence interval, 0.16 to 0.85). Monogamous women whose male partners had six or more sexual partners and were circumcised had a lower risk of cervical cancer than women whose partners were uncircumcised (adjusted odds ratio, 0.42; 95 percent confidence interval, 0.23 to 0.79). Results were similar in the subgroup of men in whom circumcision was confirmed by medical examination. Male circumcision is associated with a reduced risk of penile HPV infection and, in the case of men with a history of multiple sexual partners, a reduced risk of cervical cancer in their current female partners.

Poor oral health has been reported as a risk factor in the etiology of head and neck cancer. Data on oral health were ascertained as part of two multicenter case-control studies comprising 924 cases and 928 controls in central Europe and 2,286 cases and 1,824 controls in Latin America. Incident cases of squamous cell carcinoma of the head and neck (oral cavity, pharynx, larynx) and esophagus, as well as age (in quinquennia)- and sex frequency-matched controls, were enrolled from 1998 to 2003. Poor condition of the mouth (central Europe: odds ratio (OR) = 2.89, 95% confidence interval (CI): 1.74, 4.81; Latin America: OR = 1.89, 95% CI: 1.47, 2.42), lack of toothbrush use (Latin America: OR = 2.36, 95% CI: 1.28, 4.36), and daily mouthwash use (Latin America: OR = 3.40, 95% CI: 1.96, 5.89) emerged as risk factors for head and neck cancer, independent of tobacco use and alcohol consumption. Missing between six and 15 teeth was an independent risk factor for esophageal cancer (central Europe: OR = 2.84, 95% CI: 1.26, 6.41; Latin America: OR = 2.18, 95% CI: 1.04, 4.59). These results indicate that periodontal disease (as indicated by poor condition of the mouth and missing teeth) and daily mouthwash use may be independent causes of cancers of the head, neck, and esophagus.

Background Sexual contact may be the means by which head and neck cancer patients are exposed to human papillomavirus (HPV). Methods We undertook a pooled analysis of four population-based and four hospital-based case–control studies from the International Head and Neck Cancer Epidemiology (INHANCE) consortium, with participants from Argentina, Australia, Brazil, Canada, Cuba, India, Italy, Spain, Poland, Puerto Rico, Russia and the USA. The study included 5642 head and neck cancer cases and 6069 controls. We calculated odds ratios (ORs) of associations between cancer and specific sexual behaviours, including practice of oral sex, number of lifetime sexual partners and oral sex partners, age at sexual debut, a history of same-sex contact and a history of oral–anal contact. Findings were stratified by sex and disease subsite. Results Cancer of the oropharynx was associated with having a history of six or more lifetime sexual partners [OR = 1.25, 95% confidence interval (CI) 1.01, 1.54] and four or more lifetime oral sex partners (OR = 2.25, 95% CI 1.42, 3.58). Cancer of the tonsil was associated with four or more lifetime oral sex partners (OR = 3.36, 95 % CI 1.32, 8.53), and, among men, with ever having oral sex (OR = 1.59, 95% CI 1.09, 2.33) and with an earlier age at sexual debut (OR = 2.36, 95% CI 1.37, 5.05). Cancer of the base of the tongue was associated with ever having oral sex among women (OR = 4.32, 95% CI 1.06, 17.6), having two sexual partners in comparison with only one (OR = 2.02, 95% CI 1.19, 3.46) and, among men, with a history of same-sex sexual contact (OR = 8.89, 95% CI 2.14, 36.8). Conclusions Sexual behaviours are associated with cancer risk at the head and neck cancer subsites that have previously been associated with HPV infection.

Background: Human papillomavirus (HPV) infection is the main cause of invasive cervical cancer, but cofactors may act in conjunction with HPV. We performed a pooled analysis of seven case–control studies to examine the effect of one possible HPV cofactor, herpes simplex virus-2 (HSV-2) infection, in the etiology of invasive cervical cancer. Methods: Blood and exfoliated cervical specimens were obtained from 1263 case patients with invasive cervical cancer (1158 with squamous-cell carcinomas and 105 with adeno- or adenosquamous-cell carcinomas) and 1117 age-matched control subjects. Western blot analysis and/or an enzyme-linked immunosorbent assay were used to detect type-specific serum antibodies to HSV-2 and HSV-1, and Chlamydia trachomatis serum antibodies were detected using a micro-immunofluorescence assay. HPV DNA was detected using a polymerase chain reaction assay. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were computed from unconditional logistic regression models. Results: Overall, HSV-2 seropositivity was higher among case patients with squamous-cell carcinoma (44.4%, 95% CI = 41.5% to 47.3%) or adeno- or adenosquamous-cell carcinoma (43.8%, 95% CI = 34.2% to 53.5%) than among control subjects (25.6%, 95% CI = 23.0% to 28.2%). Cervical specimens from 1098 (94.8%) squamous-cell carcinoma case patients, 95 (90.5%) adeno- or adenosquamous carcinoma case patients, and 164 (14.7%) control subjects were positive for HPV DNA. Among the HPV DNA-positive women, HSV-2 seropositivity was associated with increased risks of squamous-cell carcinoma (OR = 2.19, 95% CI = 1.41 to 3.40) and adeno- or adenosquamous-cell carcinoma (OR = 3.37, 95% CI = 1.47 to 7.74) after adjustment for potential confounders. A similar association between HSV-2 seropositivity and squamous-cell carcinoma risk was observed after further controlling for markers of sexual behavior (OR = 1.96, 95% CI = 1.24 to 3.09). Among control subjects, HSV-2 seropositivity was associated with markers of sexual behavior, but not with cervical HPV DNA positivity. Conclusion: HSV-2 infection may act in conjunction with HPV infection to increase the risk of invasive cervical carcinoma.