Nutrition and pharyngeal cancer: results from a case-control study in Spain

[Update: Epidemiology and Prevention of Oropharyngeal Cancer]

Due to the association with the causal HPV-16 infection, the oropharyngeal carcinoma spreads into two separate entities depending on HPV-16 positivity. More recent data show a diversified picture of the importance and prevalence of the surrogate parameter p16 (discordance) for a definitive HPV-16 association, which varies worldwide. In the context of prevention options, vaccination is of major and HPV screening of healthy people only of little importance.

Association of Fried Food Intake with Gastric Cancer Risk: A Systemic Review and Meta-Analysis of Case-Control Studies

Gastric cancer is one of the most prevalent cancers in Asia, and has a significant global incidence. However, the impact of fried food consumption on gastric cancer risk remains uncertain, mainly due to the limited number of participants in previous studies. To address this knowledge gap, we aimed to examine the association between fried food intake and gastric cancer incidence through a comprehensive meta-analysis. We conducted a thorough search across multiple databases, including PubMed, EMBASE, Google Scholar, Cochrane Library, China National Knowledge Infrastructure (CNKI), Korean Information Service System (KISS), and Research Information Service System (RISS), to collect studies. The newly analyzed results of the Korean Genome and Epidemiology Study (KoGES) findings were added. We assessed integrated odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) from the selected studies using Cochrane RevMan 5.0 for the meta-analysis. The quality of the studies included in the meta-analysis was assessed using the Study Quality Assessment Tool of the National Heart, Lung, and Blood Institute (NHLBI). We included 18 studies in the analysis, which compared the impact of fried food intake in gastric cancer patients (n = 5739) and healthy adults (control, n = 70,933). There was a significant positive association between gastric cancer risk and fried food intake (OR = 1.52, 95% CI = 1.23-1.87, I2 = 76%, p = 0.0001). The relationship was found to be significant in both non-East Asians (OR = 1.48, 95% CI = 1.18-1.85, I2 = 31%, p = 0.0006) and East Asians (OR = 1.54, 95% CI = 1.14-2.08, I2 = 83%, p = 0.005). In conclusion, this meta-analysis supports the notion that fried food intake is associated with an increased risk of gastric cancer in both non-Asians and Asians. Promoting a reduction in fried food consumption as a measure against gastric cancer risk is recommended.

Fried food consumption and the risk of pancreatic cancer: A large prospective multicenter study

Background and aims

Whether fried food consumption is associated with the risk of pancreatic cancer remains elusive. We aimed to examine this association in a US population.

Methods

A population-based cohort of 101,729 US adults was identified. Fried food consumption was assessed with a validated food frequency questionnaire. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated. Explanatory analyses were conducted to identify main contributor(s) to the observed association.

Results

During an average follow-up of 8.86 years (900871.2 person-years), 402 pancreatic cancer cases occurred. High consumption of total fried foods (deep-fried plus pan-fried foods; HRquartile4 vs. 1 0.71, 95% CI 0.51-0.99, P trend = 0.047) and deep-fried foods (HRquartile 4 vs. 1 0.64, 95% CI 0.47-0.88, P trend = 0.011), but not pan-fried foods (HRquartile 4 vs. 1 0.98, 95% CI 0.73-1.32; P trend = 0.815), was found to be associated with a reduced risk of pancreatic cancer in a non-linear dose-response manner, which was not modified by predefined stratification factors and persisted in sensitivity analyses. In explanatory analyses, only chip consumption was found to be inversely associated with the risk of pancreatic cancer; consistently, the initial significant associations between total fried food and deep-fried food consumption and the risk of pancreatic cancer changed to be non-significant after omitting or further adjusting for chip consumption.

Conclusion

Consumption of deep-fried foods, but not pan-fried foods, is inversely associated with the risk of pancreatic cancer in this US population. The role of deep-fried foods in reducing the risk of pancreatic cancer appears to be mainly attributable to chips. More studies are needed to confirm our findings in other populations and settings.

The Impact of Whole Grain Intake on Gastrointestinal Tumors: A Focus on Colorectal, Gastric, and Esophageal Cancers

Cereals are one of staple foods in human diet, mainly consumed as refined grains. Nonetheless, epidemiological data indicate that whole grain (WG) intake is inversely related to risk of type 2 diabetes, cardiovascular disease, and several cancer types, as well as to all-cause mortality. Particularly responsive to WG positive action is the gastrointestinal tract, daily exposed to bioactive food components. Herein, we shall provide an up-to-date overview on relationship between WG intake and prevention of gastrointestinal tumors, with a particular focus on colorectal, stomach, and esophagus cancers. Unlike refined counterparts, WG consumption is inversely associated with risk of these gastrointestinal cancers, most consistently with the risk of colorectal tumor. Some WG effects may be mediated by beneficial constituents (such as fiber and polyphenols) that are reduced/lost during milling process. Beside health-promoting action, WGs are still under-consumed in most countries; therefore, World Health Organization and other public/private stakeholders should cooperate to implement WG consumption in the whole population, in order to reach nutritionally effective intakes.

Red Meat and Processed Meat Consumption and Nasopharyngeal Carcinoma Risk: A Dose-response Meta-analysis of Observational Studies

The purpose of this study is to clarify and quantify the potential dose-response association between the intake of total red and total processed meat and risk of nasopharyngeal carcinoma (NPC). Relevant studies were identified by searching PubMed, EMBASE, and Chinese databases (CNKI and Wanfang). The summary relative risk (RR) with 95% confidence interval (95%CI) was calculated. A total of 15 independent studies with 12,735 subjects were identified. Compared with the low-rank intake, the summary RR of NPC was 1.35 (95%CI, 1.21-1.51) for total red meat and 1.46 (95%CI, 1.34-1.64) for total processed meat. For the moderate-rank intake, the summary RR of NPC was 1.54 (95%CI, 1.36-1.79) for total red meat and 1.59 (95%CI, 1.3-1.90) for total processed meat. The summary RR for high-rank intake was 1.71 (95%CI, 1.14-2.55) for total red meat and 2.11 (95%CI, 1.31-3.42) for total processed meat. The combined estimates showed obvious evidence of statistically significant association between total red and total processed meat consumption dose and risk of NPC (Ptrend< 0.01). In conclusion, our data suggest that a high intake of total red or total processed meat is associated with a significantly increased risk of NPC.

Greater intake of fruit and vegetables is associated with lower risk of nasopharyngeal carcinoma in Chinese adults: a case-control study

PURPOSE

The effect of fruit and vegetable intake on the risk of nasopharyngeal carcinoma (NPC) remains uncertain due to limited published evidence. We performed a matched case-control study to investigate the relationship between the intake of fruit and vegetables and the risk of NPC.

METHODS

Between July 2009 and March 2011, 600 (448 male, 152 female), NPC incident cases from a single hospital in Guangzhou, Guangdong Province, China, a high-incidence area, were enrolled in the study. 600 controls, matched by gender, age (± 3 years) and household type (urban/rural) were also enrolled. Face-to-face interviews were used to collect habitual dietary intakes and information on various covariates.

RESULTS

Multivariate conditional logistic regression analyses showed significant, dose-dependent inverse associations between the intake of vegetables, fruit or a combination of the two and the risk of NPC, even after adjustments for social-economic status, body mass index, dietary factors and other potential covariates. The adjusted odds ratios (95% confidence intervals) for NPC in the top quartile of vegetable intake, fruit intake or a combination of the two, as compared to the lowest quartile, were 0.33 (0.22-0.50), 0.70 (0.47-1.04) and 0.37 (0.25-0.55), respectively. Dark green leafy vegetables, carrots, peppers and tomatoes, citrus fruit and pome fruit showed much more pronounced benefits with regards to NPC than other types of fruit and vegetables. Interaction analyses demonstrated that the effects of total combined vegetable and fruit intake were much more significant in subjects with a higher education level (p interaction: 0.027), and the benefits of fruit were observed in males, but not in females (p interaction: 0.088).

CONCLUSION

Our findings suggest that a greater consumption of fruit and vegetables may lower the risk of NPC in Chinese adults.

Dietary fiber and grain consumption in relation to head and neck cancer in the NIH-AARP Diet and Health Study

BACKGROUND

Dietary fiber and grain consumption may reduce the risk of head and neck cancer; however, the epidemiological evidence is limited. We investigated this relationship in the National Institutes of Health (NIH)-AARP Diet and Health Study.

METHODS

Cox proportional hazards models were used to calculate multivariable hazard ratios (HR) and 95% confidence intervals (CI) to investigate dietary fiber and grain intake in relation to head and neck cancer.

RESULTS

During approximately 11 years of follow-up, 1,867 (401 women/1,466 men) cases of head and neck cancer were diagnosed. Our data indicated that the relationship between fiber and grain intake and head and neck cancer is modified by sex (p-interactions < 0.001 and 0.001, respectively). Women with higher intake of total fiber and total grains had a lower risk of head and neck cancer (HR (10 g/day) = 0.77, 95% CI = 0.64-0.93; HR (serving/1,000 kcal) = 0.89, 95% CI = 0.80-0.99, respectively); this inverse relation was consistent across subtypes of fiber and grains. Conversely in men, the inverse associations were weaker and nonsignificant.

CONCLUSIONS

In the largest prospective cohort study to investigate this relation to date, intake of total fiber and grain foods was inversely associated with head and neck cancer incidence among women, but not among men.

Alcohol and the older adult: a comprehensive review

Alcohol consumption in the older adult is of major concern with the advent of baby boomers coming into the over 65-age bracket. Alcohol consumption has been touted as beneficial for health, and while that may be accurate for moderate consumption in younger persons, there is considerable risk associated with increased alcohol intake in older adults. This increase is partially due to age-related physiological changes, existing diagnoses, number of comorbid conditions, and increased use of prescribed and/or over-the-counter medications, coupled with other concerns. This review addresses the current research regarding ethanol consumption in older adults and all-cause mortality as well as several conditions more frequently seen in the geriatric population. These conditions include vascular diseases, hypertension, type 2 diabetes, gastrointestinal disorders, hepatic disorders, dental and oro-facial problems, bone density decline, and falls and fractures. In addition, drug interactions and recent research into select vitamin and mineral considerations with increased alcohol intake in older persons are addressed. While recommendations for alcohol intake have not been specifically established for age ranges within the 65-year-and-older bracket, and practitioners do not routinely assess alcohol intake or ethanol related adverse events in this population, common sense approaches to monitoring will become increasingly important as the generation of "boomers" who believe that alcohol intake improves health comes of age.

Coffee and tea intake and risk of head and neck cancer: pooled analysis in the international head and neck cancer epidemiology consortium

BACKGROUND

Only a few studies have explored the relation between coffee and tea intake and head and neck cancers, with inconsistent results.

METHODS

We pooled individual-level data from nine case-control studies of head and neck cancers, including 5,139 cases and 9,028 controls. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI), adjusting for potential confounders.

RESULTS

Caffeinated coffee intake was inversely related with the risk of cancer of the oral cavity and pharynx: the ORs were 0.96 (95% CI, 0.94-0.98) for an increment of 1 cup per day and 0.61 (95% CI, 0.47-0.80) in drinkers of >4 cups per day versus nondrinkers. This latter estimate was consistent for different anatomic sites (OR, 0.46; 95% CI, 0.30-0.71 for oral cavity; OR, 0.58; 95% CI, 0.41-0.82 for oropharynx/hypopharynx; and OR, 0.61; 95% CI, 0.37-1.01 for oral cavity/pharynx not otherwise specified) and across strata of selected covariates. No association of caffeinated coffee drinking was found with laryngeal cancer (OR, 0.96; 95% CI, 0.64-1.45 in drinkers of >4 cups per day versus nondrinkers). Data on decaffeinated coffee were too sparse for detailed analysis, but indicated no increased risk. Tea intake was not associated with head and neck cancer risk (OR, 0.99; 95% CI, 0.89-1.11 for drinkers versus nondrinkers).

CONCLUSIONS

This pooled analysis of case-control studies supports the hypothesis of an inverse association between caffeinated coffee drinking and risk of cancer of the oral cavity and pharynx.

IMPACT

Given widespread use of coffee and the relatively high incidence and low survival of head and neck cancers, the observed inverse association may have appreciable public health relevance.

Squamous carcinoma of the hypopharynx in children in Sénégal: between disarray and enigma

INTRODUCTION

The squamous carcinoma of the hypopharynx constitutes the first reason of hospitalization in our department. Different studies have been realized about it and showed an epidemiological profile characterized by the young age of the patients and the predominance of female.

OBJECTIVES

To specify the place of the children in hypopharynx cancers. To evaluate the epidemiological criteria and the difficulties in the management.

MATERIALS AND METHODS

Retrospective study of 11 years (1995-2005). Collection of the data concerning the epidemiology, clinical and paraclinical findings, the treatment, and the evolution was carried out at the University Department of Otorhinolaryngology in Dakar (Sénégal).

RESULTS

15 charts of children have been collected. They presented in the majority of the cases, an advanced cancer, with 93% of T3T4. The lesion was localized at the retro-cricoid area in 4 cases, the pyriform sinus in 3 cases, the oesophagus junction in 2 cases, and the posterior wall in 1 case. In 5 cases the lesion was spreading to the totality of the hypopharynx. No case of smoking or alcohol has been noted. The anemia has been noted in 86.7% of the cases. A case of papillomatosis of the mouth and lips has been noted. The treatment was for most of cases as symptomatic, like tracheotomy with or without gastrostomy. The evolution was fatal with 11 deaths (73.33%).

DISCUSSION

Our set is the richest set through the world of hypopharyngeal cancers in children. The Plummer-Vinson syndrome noted in 86.7% of the cases and the viral infection by HPV could play a role in the genesis of this cancer.

CONCLUSION

The cancer of the hypopharynx essentially affects the young women in Sénégal without alcohol or tobacco consumption. It does not save the children, with an awful prognosis, however. So, it is imperative to organize a vast campaign of information of the populations on the bad prognosis of this cancer and to lead a large-scale epidemiological investigation, to get a better understanding of this cancer in our country.

Human papillomavirus-16 modifies the association between fruit consumption and head and neck squamous cell carcinoma

Human papillomavirus-16 (HPV-16) is a risk factor for head and neck squamous cell carcinoma (HNSCC). HPV-positive cancers have distinct disease cofactors and improved survival following treatment. There is conflicting evidence of a protective association of fruit consumption with HNSCC. As HPV-related disease is clinically distinct, we investigated whether the association between fruit consumption and HNSCC risk was modified by exposure to HPV-16. We studied 270 cases and 493 controls with fruit intake information and known HPV-16 antibody status. Cases were identified at nine Boston-area medical facilities between 1999 and 2003. Controls were randomly selected from the greater population and frequency matched to cases by age, gender, and town of residence. Controlling for age, gender, race, smoking, alcohol, total energy intake, body mass index, and education, the seronegative individuals had a significantly lower risk of HNSCC with increasing total fruit consumption [odds ratio (OR)(tertile 2), 0.60; 95% confidence interval (95% CI), 0.38-0.95; OR(tertile 3), 0.57; 95% CI, 0.35-0.95] and specifically increasing citrus fruit consumption (OR(tertile 2), 0.61; 95% CI, 0.39-0.97; OR(tertile 3), 0.59; 95% CI, 0.37-0.96). However, among the seropositive, risk increased with greater fruit consumption (OR(tertile 2), 2.27; 95% CI, 0.92-5.58; OR(tertile 3), 1.40; 95% CI, 0.55-3.59) and citrus fruit consumption (OR(tertile 2), 3.35; 95% CI, 1.36, 8.24; OR(tertile 3), 3.15; 95% CI, 1.23-8.08). This interaction was statistically significant (P < 0.05), showing that fruit consumption was associated with a reduced HNSCC risk among HPV-16-seronegative individuals but an increased HNSCC risk among the HPV-16-seropositive individuals. These findings suggest that dietary factors dramatically alter the pattern of occurrence of HPV-associated HNSCC and show that viral-related disease is clinically and etiologically distinct.

[Dietary factors and oral cancer: a case-control study in Greater Metropolitan São Paulo, Brazil]

Dietary factors associated with oral cancer were investigated in a case-control hospital-based study in the city of São Paulo, Brazil, from 1998 to 2002. A total of 835 subjects, 366 with histologically confirmed incident cases of oral-cavity or pharyngeal cancer and 469 controls participated in the study. Dietary data were collected with a food frequency questionnaire (FFQ). Odds ratios (OR) and 95% confidence intervals (95%CI) were obtained from unconditional logistic regression, adjusted for potential confounders. Inverse associations with risk of oral cancer were found for the highest intake of beans, OR = 0.37 (95%CI: 0.22-0.64), raw vegetables, OR = 0.51 (95%CI: 0.29-0.93) and the intermediate tertile of rice and pasta intake, OR = 0.56 (95%CI: 0.38-0.83). Positive associations were observed for the highest intake of eggs, OR = 1.84 (95%CI: 1.23-2.75), potatoes, OR = 2.22 (95%CI: 1.53-3.25), and milk, OR= 1.80 (95%CI: 1.09-2.98). Some traditional Brazilian foods like rice and beans emerged as protective factors against oral cancer, independently of other risk factors.

Milk, dairy products and cancer risk (Italy)

BACKGROUND

Inconclusive information is available on the potential role of milk and dairy products on the risk of cancer at several sites.

METHODS

We analyzed data from a large and integrated network of hospital-based case-control studies in Italy on cancers of the oral cavity and pharynx (598 cases, 1491 controls), oesophagus (304 cases, 743 controls), colorectum (1953 cases, 4154 controls), larynx (460 cases, 1088 controls), breast (2569 cases, 2588 controls), ovary (1031 cases, 2411 controls) and prostate (1294 cases, 1451 controls).

RESULTS

Multivariate odds ratio (OR) for the highest consumption level of any type of milk was 0.94 (95% confidence interval, CI: 0.61-1.33) for cancers of the oral cavity and pharynx, 1.20 (95% CI: 0.76-1.90) for oesophageal, 0.77 (95% CI: 0.62-0.96) for colon, 0.80 (95% CI: 0.60-1.05) for rectal, 0.83 (95% CI: 0.56-1.21) for laryngeal, 0.91 (95% CI: 0.76-1.10) for breast, 0.89 (95% CI: 0.68-1.15) for ovarian and 1.08 (95% CI: 0.84-1.37) for prostate cancer. A significant trend in risk was found for colon cancer only. Inverse associations were observed between consumption of skim milk and cancers of colon (OR=0.84; 95% CI: 0.73-0.97), rectum (OR=0.76; 95% CI: 0.64-0.91), breast (OR=0.87; 95% CI: 0.77-0.98) and ovary (OR=0.77; 95% CI: 0.66-0.91). Conversely, whole milk consumption was directly associated with cancer of the rectum (OR=1.22; 95% CI: 1.03-1.44) and ovary (OR=1.25; 95% CI: 1.07-1.46). High consumption of cheese was inversely related to colon cancer risk (OR=0.80; 95% CI: 0.67-0.95).

CONCLUSIONS

There was a modest direct association between milk and dairy products and prostate cancer, and a moderate inverse one for colorectal cancer. However, our findings indicate that milk and dairy products are not strong risk indicators for any of the cancers considered.

Case-control study of oropharyngeal cancer

BACKGROUND

In order to test some hypotheses of risk factors for oropharyngeal cancer (neoplasm of base of tongue, palate and tonsils) matched case-control study was conducted in Belgrade, Serbia and Montenegro, during the period 1998-2000.

METHODS

Study comprised 100 incidence cases with oropharyngeal cancer and 100 controls with some non-malignant diseases of head and neck.

RESULTS

According to multivariate analysis, ever smoking, interaction between smoking and alcohol consumption, and occupational exposure to wood dust were found to be independent risk factors for oropharyngeal cancer (odds ratio-OR=5.10 95% confidence intervals-95% CI=1.70-15.27, OR=2.61 95% CI=1.54-4.41, and OR=4.16 95% CI=1.45-11.91, respectively).

CONCLUSION

The results of the present study are in line with other authors' findings showing that smoking and alcohol consumption are the main risk factors for oropharyngeal cancer. The effect of occupational exposure to wood dust warrants further investigation.

Dietary folate is associated withp16INK4A methylation in head and neck squamous cell carcinoma

Inactivation of the p16(INK4A) (CDKN2A) gene in the Rb pathway is among the most common somatic alterations observed in tobacco-related solid tumors, including head and neck squamous cell carcinoma (HNSCC). In addition, a low folate diet is an important risk factor for HNSCC. Decreased dietary folate in an animal model of hepatocellular carcinoma has been associated with the induction of epigenetic silencing of the p16(INK4A) gene. In an ongoing population-based study of HNSCC, we sought to extend this observation to human disease testing the hypothesis that p16(INK4A) methylation is associated with decreased dietary folate. We also investigated the association of methylation silencing with functional polymorphisms in the folate metabolism enzyme methylene tetrahydrofolate reductase (MTHFR). In 169 HNSCCs, the odds ratio for p16(INK4A) methylation among those with low dietary folate intake was 2.3 (95% CI = 1.1-4.8) when compared with those with high folate intake. Furthermore, this increased risk for epigenetic silencing at p16(INK4A) was modified by the MTHFR alleles previously associated with diminished serum folate levels. Hence, in HNSCC low dietary intake of folate is associated with p16(INK4A) methylation, and this relationship is modified by the MTHFR genotype. Our data provides important evidence for a mechanism of action of folate deficiency in cancer.

Clinicopathological study of head and neck cancers in Ilorin, Nigeria

Eighty-nine cases of head and neck cancers were studied over a 5-year period (1997--2001) at the University of Ilorin Teaching Hospital, Nigeria. The most common cancer affecting the head and neck region was carcinoma which constituted 70.8% of all the cases studied. It was followed by the lymphomas and blastomas which accounted for 20.2% and 9%, respectively. The nose/paranasal sinuses were the most common site of primary cancer (18%) followed by thyroid (12.4%), nasopharynx (11.3%) and larynx (4.5%). Other sites include a hypopharynx (3.4%), eye (2.2%), palate (2.2%), tongue (2.2%), skin (1.1%), lip (1.1%), salivary gland (1.1%), oropharynx (1.1%). Cervical lymph node metastasis with unknown primary lesion was seen in 10.1%. The peak age incidence was in the fifth decade of life. The improvement in locoregional control of head and neck cancers over the last decades does not appear to modify the final survival of these patients. It is crucial to understand as accurately as possible the risk factors for these malignancies in order to improve primary prevention.

Raw versus Cooked Vegetables and Cancer Risk

This review of the medical literature from 1994 to 2003 summarizes the relationship between raw and cooked vegetables and cancer risk and examines whether they may affect cancer risk differently. Twenty-eight studies examined the relationship between raw and cooked vegetables and risk for various cancers. Twenty-one studies assessed raw, but not cooked, vegetables and cancer risk. The majority of these assessed risk of oral, pharyngeal, laryngeal, esophageal, lung, gastric, and colorectal cancers. Most showed that vegetables, raw or cooked, were inversely related to these cancers. However, more consistent results were found for oral, pharyngeal, laryngeal, esophageal, and gastric cancers. Nine of the 11 studies of raw and cooked vegetables showed statistically significant inverse relationships of these cancers with raw vegetables, but only 4 with cooked vegetables. The few studies of breast, lung, and colorectal cancers also suggested an inverse relationship with both raw and cooked vegetables, but these results were less consistent. In the two studies of prostate cancer, there was no association with either raw or cooked vegetables. One of two bladder cancer studies found an inverse relationship with cooked, but not raw, vegetables. Possible mechanisms by which cooking affects the relationship between vegetables and cancer risk include changes in availability of some nutrients, destruction of digestive enzymes, and alteration of the structure and digestibility of food. Both raw and cooked vegetable consumption are inversely related to epithelial cancers, particularly those of the upper gastrointestinal tract, and possibly breast cancer; however, these relationships may be stronger for raw vegetables than cooked vegetables.

Nutrition and head and neck cancer

The role of nutrition in patients with head and neck cancer, specifically squamous cell carcinoma, is underappreciated. The composition of the diet can contribute to carcinogenesis, and specific nutrients may offer some protection in the presence of known carcinogens (ie, tobacco). Patients with head and neck cancer are frequently malnourished, which may have prognostic implications for the morbidity and outcome of therapies. Although the benefits of preoperative nutritional supplementation have been demonstrated only in severely malnourished patients, the use of immune-enhancing formulas may prove to be beneficial. Special consideration should be given to the nutritional needs and possible interactions of diet and therapy in patients receiving radiation and chemotherapy. Physicians should be cognizant of the widespread use of alternative diets and nutritional supplements that can be harmful and may interact with standard treatments. New knowledge regarding the role of nutrition in cancer offers hope for the nutritional chemoprevention of head and neck cancers.