The epidemiology of mouth cancer: a review of global incidence

Oral cancer: experiences and diagnostic abilities elicited by dentists in North-western Spain

BACKGROUND

Opinions, knowledge, behaviours and attitudes of general dental practitioners on oral cancer prevention and detection have been reported from many countries. However, experiences and skills of oral cancer detection have not been evaluated systematically.

OBJECTIVE

To obtain information on behaviours of screening and ability to correctly detect oral cancer and precancer among general dentists (GDP) in North-western Spain.

SUBJECTS AND METHODS

Thirty-two randomly selected GDPs completed questionnaires and then classified 50 projected images of clinical lesions, into cancer, precancer or benign lesions.

RESULTS

87.5% reported conducting routine oral examinations, 84.4% provided routine advice to their subjects for risk modifications and 84.4% claimed to biopsy a suspected oral mucosal lesion that they detected in practice. In a quasi research setting using clinical slides, the sensitivity of visual diagnosis of a cancerous lesion was 61.4% and precancer 59.5%. The diagnostic accuracy reported here is lower than what is already reported by evaluation of published screening programmes by dentists.

CONCLUSIONS

Our data from Spain suggest a need for improving the diagnostic ability of GDPs in the visual detection of oral cancer/precancer by strengthening continuing professional education.

A minimally invasive immunocytochemical approach to early detection of oral squamous cell carcinoma and dysplasia

Squamous dysplasia of the oral cavity indicates increased risk of progression to squamous cell carcinoma (SCC). An important advance would be the development of a minimally invasive assay for identification of oral SCC and dysplasia. We have investigated the suitability in this context of immunostaining oral smears for minichromosome maintainance proteins (MCMs), sensitive and specific biomarkers of cell cycle entry. Immunohistochemical examination of 66 oral tissue samples showed a greater frequency of Mcm-2 expression in surface layers of moderate/severe dysplasia and SCC compared to benign keratosis/mild dysplasia. Immunocytochemistry for Mcm-2/Mcm-5 was performed on 101 oral smears. Conventional smears included 23 from normal mucosa, benign proliferative disease and mild dysplasia, all of which were MCM negative. Of 52 conventional smears of SCC tissue samples, 18 were inadequate. However, MCM-positive cells were present in 33/34 adequate samples. Of 26 liquid-based cytology smears, 19 out of 20 smears from SCC were adequate and all were MCM positive. Six smears from benign lesions were adequate and MCM negative. We conclude that MCMs are promising markers for early detection of oral SCC and dysplasia, particularly in a liquid-based cytology platform. Detection of MCMs would be amenable to automation and potentially applicable in the developing world. Further studies are now warranted.

Gingival Squamous Cell Carcinoma: Diagnostic Delay or Rapid Invasion?

BACKGROUND

The similarity between gingival squamous cell carcinoma (GSCC) and more common periodontal lesions may lead to a delay in diagnosis or misdiagnosis. Neoplastic lesions of gingival tissues are frequently diagnosed at an advanced stage.

METHODS

To assess the relative time from when patients first become aware of the problem to histopathologic diagnosis (total diagnostic time), 59 consecutive oral cancer cases were examined in this study. The following variables were considered: age, gender, smoking habits, tumor stage at diagnosis, and total diagnostic time. The median of the patients' total diagnostic time (1.5 months) was used as a cutoff point to distinguish between delayed and non-delayed cases. Analysis of the variables was undertaken using the Student t test and chi2 test, with a 95% confidence interval (CI).

RESULTS

The total diagnostic time was <1.5 months for 75% of gingival carcinomas, 50% of tongue carcinomas, and 78% of floor-of-the-mouth carcinomas. It was >1.5 months for 25% of gingival carcinomas, 50% of tongue carcinomas, and 21% of floor-of-the-mouth carcinomas. No significant differences in time before diagnosis were found when gingival cancers were compared to other oral tumors (chi2=0.21; 95% CI=-0.40 to 0.26). However, by the time of diagnosis, gingival cancers had invaded adjacent structures more frequently than other oral cancers (chi2=13.51; 95% CI=0.18 to 0.85).

CONCLUSIONS

The gingival location of oral squamous cell carcinoma (OSCC) was associated with advanced stages at the time of diagnosis, due to early invasion of contiguous bone tissue (T4-primary tumor). This would indicate that even earlier referral and diagnosis are necessary.

An Overview of Epidemiology and Common Risk Factors for Oral Squamous Cell Carcinoma

Understanding the epidemiologic picture and the risk factors for oral cancer can help identify and treat patients at risk for oral cancers. Early diagnosis of an oral cancer continues to be important to achieving a favorable prognosis. Absent a diagnosis of oral/pharyngeal cancer, there clearly can-lot be an effective treatment plan. Discovering a potentially malignant or malignant lesion and through biopsy reaching a diagnosis for the lesion begins by performing an examination with the purpose of detecting oral/pharyngeal lesions. An oral cancer screening can be performed in less than five minutes without any expensive diagnostic aids. Despite the ease with which this exam can be performed and the noninvasive nature of the examination,most patients report that they have never had an oral cancer examination. Late stage diagnosis continues to be a common situation resulting in high rates of morbidity and mortality. Without early recognition it seems that the trend of late stage diagnosis will continue. Physicians, dentists, and other health care providers should be performing the oral cancer screening examination on a routine basis for all of their patients.Note: For the interested clinician, the author highly recommends an excellent comprehensive text on the subject of oral cancer. Sol Silverman's(with multiple contributors) The American Cancer Society's Atlas of Clinical Oncology Oral Cancer: Fifth Edition by BC Decker Publishers is an excellent overview of oral cancer covering in greater detail many of the subjects that could not be covered in this brief article. Additionally, there are excellent color photographs of the common presentations of oral malignancies that can be helpful in assessing oral/pharyngeal lesions.

Squamous cell carcinoma of the oral cavity, maxillary antrum and lip in a Zimbabwean population: A descriptive epidemiological study

Squamous cell carcinoma accounts for approximately 90% of oral malignancies. The objective of this study was to document the gender, age, sub-site distribution and histologic differentiation of squamous cell carcinoma of the oral cavity, maxillary antrum and lip in a Zimbabwean population. Hospital records of patients with a histologic diagnosis of squamous cell carcinoma of the oral cavity, maxillary antrum and lip seen at Harare Central Hospital and Parirenyatwa Hospital in Zimbabwe during the period January 1982-December 1991 were reviewed. 20.8% (n = 358/1723) were squamous cell carcinoma of the oral cavity, maxillary antrum and lip. Age ranged from 3 to 70years with a 2:1 male:female ratio. Peak incidence in both sexes were in the 41-50 and 51-60years age groups. Sub-site distribution was mandibular gingiva 18.4%, tongue 17.9%, floor of the mouth 16.2%, maxillary gingiva 9.2%, buccal mucosa 9.2%, maxillary antrum 12.6%, hard palate 7.8%, soft palate 4.8%, lower lip 2.8% and upper lip 1.1%. 64.8% were well differentiated, 24.8% moderately differentiated and 10.4% poorly differentiated. The mandibular gingiva, floor of the mouth and tongue were most commonly affected. Lip squamous cell carcinoma was uncommon. Well-differentiated squamous cell carcinoma was most common in the 41-60 years age group.

Comparative evaluation of the chemopreventive efficacy of green and black tea polyphenols in the hamster buccal pouch carcinogenesis model

OBJECTIVES

To evaluate the comparative chemopreventive efficacy of green tea polyphenols (Polyphenon-E) and black tea polyphenols (Polyphenon-B) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis.

DESIGN AND METHODS

Hamsters were divided into 6 groups. Animals in group 1 served as controls. Animals in groups 2 and 3 were administered 0.05% Polyphenon-E and B, respectively, in the diet. The right buccal pouches of animals in groups 4-6 were painted with 0.5% DMBA three times a week for 14 weeks. While group 4 received no further treatment, hamsters in groups 5 and 6 received diet containing 0.05% Polyphenon-E and B, respectively. The status of carcinogen-metabolising enzymes, lipid peroxidation and glutathione-dependent antioxidants in the buccal pouch and liver, as well as the frequency of bone marrow micronuclei were used as biomarkers.

RESULTS

Application of DMBA induced HBP carcinomas, increased genotoxicity with an imbalance in carcinogen-metabolising enzymes and the cellular redox status. Inhibition of HBP carcinomas by Polyphenon-E and B was associated with a significant decrease in phase I enzymes, modulation of lipid peroxidation and enhanced antioxidant and phase II enzyme activities.

CONCLUSION

The greater efficacy of Polyphenon-B in inhibiting HBP carcinogenesis suggests that it may have a major impact in the chemoprevention of oral cancer.

Strong association between infection with human papillomavirus and oral and oropharyngeal squamous cell carcinoma: a population-based case-control study in southern Sweden

CONCLUSIONS

The results of this study demonstrate a strong association between infection with high-risk types of human papillomavirus (HPV) and oral and oropharyngeal squamous cell carcinoma (OOSCC), suggesting that high-risk HPV types play a key role in carcinogenesis. The estimated proportion of OOSCC cases attributable to HPV infection was 35%.

OBJECTIVE

HPV appears to have an aetiological role in OOSCC, despite the fact that the reported prevalences of HPV in both OOSCC patients and healthy individuals have varied widely. We aimed to investigate the presence and spectrum of both high- and low-risk HPVs in all consecutive cases of OOSCC in a Swedish healthcare region over a 3-year period and in population-based, matched healthy controls.

MATERIAL AND METHODS

A total of 131 patients with OOSCC were studied. Samples taken from the surface of the tumour and from the tonsillar fossa using cotton-tipped swabs were investigated, together with exfoliated cells collected using a mouthwash. Tonsillar fossa and mouthwash specimens were collected in the same way from 320 matched controls. All samples were tested for HPV DNA by nested polymerase chain reaction using the primer pairs MY09/MY11 and GP5 + /GP6+, and in positive cases the HPV type was determined by DNA sequencing.

RESULTS

Infection with high-risk HPV was shown to be a strong risk factor for OOSCC (OR = 63; 95% CI 14-480). Forty-seven (36%) of the cancer patients had > or =1 specimen that was positive for a high-risk HPV type (81% of which were HPV 16), while only 3 (0.94%) of the controls were positive for a high-risk HPV type. Seven (5.3%) of the cancer patients and 13 (4.1%) of the controls were positive for any of the mucosal, mucocutaneous or cutaneous low-risk HPV types.

Prognostic factors in intraoral squamous cell carcinoma: the influence of histologic grade

PURPOSE

The purpose of this retrospective study was to review the outcome of patients with oral cavity squamous cell carcinoma treated at a single institution by primary surgical resection with or without adjuvant radiotherapy or chemoradiotherapy and to identify factors affecting survival and locoregional control.

PATIENTS AND METHODS

The records of 233 patients with oral cavity squamous cell carcinoma treated at a single institution from 1993 to 2003 were identified from the Legacy Emanuel Hospital and Health Center's cancer registry (Portland, OR). All patients undergoing surgical resection as a primary treatment modality were included in the study. Patients with nonresectable disease, distant metastasis, and those with inadequate follow-up data were excluded from the study. Patients with positive surgical margins, high-grade histology, aggressive biologic behavior, or advanced staged disease underwent adjuvant radiotherapy or chemoradiotherapy. The data collected included age, gender, race, tumor site, margin status, grade, TNM stage, cancer therapies, and cancer status. Data were statistically analyzed in an attempt to identify predictors of locoregional control and disease-free survival. Descriptive statistics were calculated for each variable and survival was calculated using the Kaplan-Meier method. Prognostic factors were analyzed using the Cox proportional hazard model.

RESULTS

Two hundred fifteen patients consisting of 119 men (55%) and 123 females (52%), with an average age at diagnosis of 66 years (SD +/- 14), met the criteria for inclusion in the study. Average tumor size was 23.5 mm (SD +/- 14.1). Overall 5-year survival was 56% and disease-free survival at 5 years was 58%. Stage and grade were identified as having a statistically significant effect on survival (P = .014; likelihood ratio chi-square = 10.7, 3 degrees of freedom; and P = .026; likelihood ratio chi-square = 5, 1 degree of freedom, respectively). Neither age, gender, race, tumor site, nor positive margins showed a statistically significant effect on survival (P > .05).

CONCLUSION

This study highlights the importance of grade and stage as independent factors in predicting survival in patients with oral squamous cell carcinoma.

Oral status, oral infections and some lifestyle factors as risk factors for oral and oropharyngeal squamous cell carcinoma. A population-based case-control study in southern Sweden

CONCLUSION

Our results show that average and poor oral hygiene and inadequate dental status are independent risk factors for oral and oropharyngeal squamous cell carcinoma (OOSCC), irrespective of tobacco and alcohol consumption.

OBJECTIVE

To evaluate a possible relationship between oral cancer, oral hygiene, dental status, oral mucosal lesions and some lifestyle factors in a population-based case-control study.

MATERIAL AND METHODS

Between September 2000 and January 2004, 132/165 (80%) of all incident cases of OOSCC and 320/396 (81%) of the intended eligible matched controls participated in the study. Cases and controls were subjected to an identical oral examination. A standardized protocol specially designed for the study was used.

RESULTS

After adjusting for tobacco and alcohol consumption, average oral hygiene (OR 2.0; 95% CI 1.1-3.6) and poor oral hygiene (OR 5.3; 95% CI 2.5-11.3) emerged as significant risk factors for OOSCC. More than 20 lost teeth (OR 3.4; 95% CI 1.4-8.5), >5 defective teeth (OR 3.1; 95% CI 1.2-8.2) and poorly fitting or defective complete dentures (OR 3.8; 95% CI 1.3-11.4) were significant risk factors. Regular dental check-ups were associated with a decreased risk of OOSCC (OR 0.4; 95% CI 0.2-0.6).

Oral malignant neoplasia: a survey of 428 cases in two Zimbabwean hospitals

A review of oral malignant neoplasms biopsies accessioned in the pathology services of Harare Central Hospital and Parirenyatwa Hospital, Harare, Zimbabwe, during the 10year period January 1982 to December 1991 was carried out. Clinical records of 428 patients with histologically diagnosed oral malignant neoplasms by ICD-O type and site (COO.O-CO6.9) were retrieved and analyzed for gender, age, history of tobacco and alcohol usage, neoplastic type and histologic differentiation of squamous cell carcinoma (8000/3). Oral malignant neoplasms constituted 24.8% (n = 428) of the 1723 biopsies accessioned in the department during this period. There was a male to female ratio of 1.9:1, with lesions being most common in the 41-60 year age group. Squamous cell carcinoma, (8070/3) 73.1%, was the predominant oral malignancy most common in the 61-70 year age group with 21.1% on the mandibular gingivae (CO3.1), 20.5% on the tongue (CO1.9-CO2.9), 18.5% on the floor of the mouth (CO4.9) and 10.5% each on the maxillary gingivae (CO3.O) and buccal mucosa (CO6.O). The hard palate (CO5.9) had 9% of the lesions. Lip malignancy (COO-COO.9 and C44.0), inclusive of mucosa of lip, vermilion and skin, constituted 3.3% and minor salivary gland (CO6.9) malignancy (M-8940/3) 4.9%. The remaining oral malignancies, 11%, included Burkitt's lymphoma (M-9687/3) 4.7%; Kaposi's sarcoma (M-9140/3) 3.7%; osteosarcoma (M-9180/3) 2.6% and malignant melanoma (M-8720/3) 1.9%. Fourty five percent of the patients admitted tobacco and alcohol consumption, of whom 95% were males. Oral malignant neoplasms were more common in males than females and occurred in a relatively young age group. Well-differentiated squamous cell carcinoma (M-8070/31) was the most common oral malignant neoplasm and was most frequently found on the mandibular gingivae (CO3.1), tongue (CO1.9-CO2.9) and floor of the mouth (CO4.9). The lip (COO-COO.9) was least affected with a high palatal (CO5.9) involvement.

Alterations of Rb Pathway Components Are Frequent Events in Patients with Oral Epithelial Dysplasia and Predict Clinical Outcome in Patients with Squamous Cell Carcinoma

OBJECTIVE

This study was designed to test the hypothesis that alterations in expression of G1/S modulators cyclin D1, p16 and pRb occur in patients with oral epithelial dysplasia, considered to be at increased risk for malignant transformation. In addition, the analysis of expression of all three markers in the same set of oral cancer patients would provide a unique opportunity to determine whether these alterations have cooperative or synergistic effects on oral cancer development and prognosis.

PATIENTS AND METHODS

A prospective study was undertaken to carry out immunohistochemical analysis of cyclin D1, p16 and pRb proteins in serial paraffin-embedded tissue sections of 220 oral squamous cell carcinomas (OSCCs), 90 potentially malignant lesions (52 oral hyperplastic lesions, 38 dysplasias) and 81 matched histologically normal oral tissues and correlated them with clinicopathological parameters. Ninety-eight OSCC patients were followed up for a maximum period of 94 months with overall median survival of 21 months.

RESULTS

Seventy-five of 90 (83%) potentially malignant lesions and 198 of 220 (90%) OSCCs showed altered expression of at least one of the proteins in the pRb pathway, while 10 of 90 (11%) patients with potentially malignant lesions and 40 (18%) of 220 OSCC patients showed all three alterations. Loss of p16 was the earliest event in oral tumorigenesis. In a multivariate model, loss of pRb was associated with transition from hyperplasia to dysplasia (OR = 3.727, p = 0.005). The transition of potentially malignant lesions to malignant stage was associated with pRb-/cyclin D1+ phenotype (OR = 2.294, p = 0.001) and p53+ phenotype (OR = 2.230, p = 0.002). Loss of pRb and accumulation of p53 (pRb-/p53+) phenotype was associated with histologic progression of the tumors and acquisition of invasive potential. Multivariate analysis using Cox's proportional hazards model revealed that pRb-/p53+ phenotype was the most significant adverse prognosticator for disease-free survival (hazards ratio, (HR) = 2.642, p = 0.004).

CONCLUSIONS

Deregulation of the p16/pRb/cyclin D1 pathway is an early event in acquisition of dysplasia, but deregulation of both pRb and p53 pathways is associated with malignant transformation and adverse prognosis in oral tumorigenesis.

Phenotypic alterations in Rb pathway have more prognostic influence than p53 pathway proteins in oral carcinoma

The two well-defined pathways that are shown to be prominently altered in a variety of cancers are the cell cycle regulatory pathways led by either p53 or Rb genes. The present study is undertaken to find the pathway that is more altered in oral carcinoma at protein level, with special emphasis on its prognostic significance. The expression pattern of key molecules of the Rb and p53 pathways, such as Rb, cyclin D1, CDK4, p16, p53, p21 and Bcl-2 and the proliferative marker PCNA were analysed in 348 oral carcinoma specimens by immunohistochemical technique. The expression index of these molecules and various clinicopathological factors were statistically correlated with treatment end points to assess its prognostic efficacy after following up these patients up to a maximum of 48 months with a median of 23 months. Rb pathway proteins, Rb (P=0.016), cyclin D1 (P=0.0001) and p16 (P=0.012) showed significant association with disease-free survival, and p16 (P=0.041) and cyclin D1 (P=<0.0001) with the overall survival. Among p53 pathway proteins studied, only p53 expression index showed association with both disease-free survival and overall survival. Multivariate analyses confirmed that the biological variables, cyclin D1 and p16 and the clinical variable, 'stage of disease' were independent predictors of disease-free survival and overall survival. Subgrouping of the patients on the basis of p16 and cyclin D1 expression revealed that the subgroup having downregulation of p16 and overexpression of cyclin D1 exhibited the worst disease-free survival and overall survival compared to the other subgroups. The present data showed that disabling of the Rb and p53 pathways were frequent events in oral carcinoma. The study also demonstrated that the Rb pathway proteins are comparatively more important than p53 pathway proteins for the prognostication of oral carcinoma patients. The combined evaluation of p16 and cyclin D1 in oral carcinoma could identify a group of patients with the worst survival who might therefore need alternate or more intense treatment strategies.

Epidemiology of head and neck cancer: magnitude of the problem

Head and neck cancer comprises squamous cell carcinomas of the upper aerodigestive tract. There are similarities in their natural history, epidemiology and control. For these cancers premalignant changes can be identified. Smoking and drinking are the major risk factors. The geographical variations in incidence and mortality are indicative of differences in the prevalence of risk factors between countries. The dramatic increase in head and neck cancers is cause for great concern, particularly in Central-Eastern Europe. The great majority of these cancers could be prevented by reducing the prevalence of established risk factors. Screening could be used to detect both precancerous lesions and early invasive cancers; however, no study as yet has demonstrated a reduced incidence and mortality resulting from screening. When setting strategies for prevention, the socioeconomic differentials in incidence and mortality from head and neck cancers need to be taken into account.

"Scheduling delay" in oral cancer diagnosis: a new protagonist

Diagnostic delays in oral cancer have been classified as "patient delay" and "delay by the clinicians". However, the influence of the accessibility (scheduling delay) to the health care system in oral cancer diagnosis has not been studied before. To assess scheduling delay, a descriptive, cross-sectional study was designed. This study was based upon role-play telephone conversations with two standardised patients (lingual ulceration-SP1 and patient seeking fixed prosthodontics-SP2). that followed a structured script. The variables considered in the study were days to go until the arranged appointment, professional degree of the contacted person and referral to other provider of care. The scheduling delay for SP1 reached a median value of 1 day, and for SP2 was 6 days. When the professional degree (receptionist vs GDP) of the person arranging the appointment for the patient with lingual ulceration was considered, the scheduling delay was significantly shorter when the appointment was fixed by the GDP (X approximately i-X approximately j=4.5; 95%CI=-7.48,-1.51). GDPs gave priority to the patients with lingual ulcerations over those demanding fixed bridgework (X approximately i-X approximately j=6.48; 95%CI=-9.46,-3.50). The GDPs showed a high level of awareness of the oral cancer, however, educational interventions seem to be necessary for dental surgery receptionists.

Therapeutic efficacy of green tea polyphenols on cellular thiols in 4-Nitroquinoline 1-oxide-induced oral carcinogenesis

In cancer, a high flux of oxidants not only depletes the cellular thiols, but damages the whole cell as well. Epidemiological studies suggest green tea may mitigate cancers in human and animal models for which several mechanisms have been proposed. In the present investigation, the levels of cellular thiols such as reduced glutathione (GSH), oxidised glutathione (GSSG), protein thiols (PSH), total thiols, lipid peroxidation product conjugated dienes and the activity of gamma glutamyl transferase (GGT) were assessed in tongue and oral cavity. In 4-Nitroquinoline 1-oxide- (4-NQO) induced rats, there was a decrease in the levels of GSH, PSH and total thiols and an increase in the levels of GSSG, conjugated dienes and the activity of GGT. On supplementation of green tea polyphenols (GTP) for 30 days (200 mg/kg) for the oral cancer-induced rats, there was a moderate increase in the levels of GSH, PSH and total thiols and a decrease in the levels of GSSG, conjugated dienes and the activity of GGT. Thus, GTP reduces the oxidant production thereby maintains the endogenous low molecular weight cellular thiols in oral cancer-induced rats. From the results, it can be concluded that GTP supplementation enhances the cellular thiol status thereby mitigate oral cancer.

Tobacco-specific nitrosamines in smokeless tobacco products marketed in India

Smokeless tobacco products are a known cause of oral cancer in India. Carcinogenic tobacco-specific nitrosamines in these products are believed to be at least partially responsible for cancer induction, but there have been no recent analyses of their amounts. We quantified levels of 4 tobacco-specific nitrosamines, N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in 32 products marketed currently in India. Levels of nitrate, nitrite and nicotine were also determined. The highest levels of tobacco-specific nitrosamines were found in certain brands of khaini, zarda and other smokeless tobacco products. Concentrations of NNN and NNK in these products ranged from 1.74-76.9 and 0.08-28.4 microg/g, respectively. Levels of tobacco-specific nitrosamines in gutka were generally somewhat lower than in these products, but still considerably higher than nitrosamine levels in food. Tobacco-specific nitrosamines were rarely detected in supari, which does not contain tobacco, or in tooth powders. The results of our study demonstrate that exposure to substantial amounts of carcinogenic tobacco-specific nitrosamines through use of smokeless tobacco products remains a major problem in India.

Ethanolic leaf extract of neem (Azadirachta indica) inhibits buccal pouch carcinogenesis in hamsters

We evaluated the chemopreventive effects of ethanolic neem leaf extract in the initiation and post-initiation phases of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. The frequency of bone marrow micronuclei as well as the concentrations of lipid peroxides, ratio of reduced to oxidized glutathione (GSH/GSSG), and the activities of the GSH-dependent enzymes glutathione peroxidase (GPx) and glutathione-S-transferase (GST) in the buccal pouch, liver and erythrocytes were used as biomarkers of chemoprevention. All the hamsters painted with DMBA alone for 14 weeks developed buccal pouch carcinomas that showed diminished lipid peroxidation and enhanced antioxidant status associated with increased frequencies of bone marrow micronuclei. In the liver and erythrocytes of tumour-bearing animals, enhanced lipid peroxidation was accompanied by compromised antioxidant defences. Administration of ethanolic neem leaf extract effectively suppressed DMBA-induced HBP carcinogenesis as revealed by the absence of tumours in the initiation phase and reduced tumour incidence in the post-initiation phase. In addition, ethanolic neem leaf extract modulated lipid peroxidation and enhanced antioxidant status in the pouch, liver and erythrocytes and reduced the incidence of bone marrow micronuclei. The results of the present study, demonstrate that ethanolic neem leaf extract inhibits the development of DMBA-induced HBP tumours by protecting against oxidative stress.

Attenuated type II TGF-beta receptor signalling in human malignant oral keratinocytes induces a less differentiated and more aggressive phenotype that is associated with metastatic dissemination

We examined the effect of stable transfection of dominant negative TbetaR-II (dn TbetaR-II) cDNA in a human oral carcinoma cell line that contained normal Ras and was growth inhibited by TGF-beta1. Two clonal cell lines containing dn TbetaR-II were isolated and compared to the vector-only control and parent cell line. The treatment of cells with exogenous TGF-beta1 resulted in a decrease in ligand-induced growth inhibition and loss of c-myc downregulation in test cells compared to controls; transcriptional activation of certain genes including fra-1 and collagenase was retained. Cells containing dn TbetaR-II grew faster in monolayer culture, expressed less keratin 10 and exhibited increased motility and invasion in vitro compared to control cell lines. Endogenous TGF-beta1 production and the regulation of MMP-2 and MMP-9 by TGF-beta1 remained unchanged. After orthotopic transplantation to the floor of the mouth in athymic mice, cells containing dn TbetaR-II formed comparable numbers of primary tumours at the site of inoculation as controls but the tumours were less differentiated as demonstrated by the absence of keratin 10 immunostaining. Further, metastatic dissemination to the lungs and lymphatics was more evident in grafts of cells containing dn TbetaR-II than controls. Taken together, the results demonstrate that attenuation of TGF-beta signalling through transfection of dn TbetaR-II cDNA leads to an enhanced growth rate, a loss of tumour cell differentiation and an increase in migration and invasion, characteristics that corresponded to the development of the metastatic phenotype.

Is the incidence of oral and pharyngeal cancer increasing in Finland? An epidemiological study of 17 383 cases in 1953-1999

OBJECTIVE

The aim of this study was to describe the occurrence of oral and pharyngeal cancer in Finland over the last half century.

MATERIALS AND METHODS

The study included all lip, oral and pharyngeal cancer cases diagnosed in Finland and reported to the nation-wide Finnish Cancer Registry between 1953 and 1999.

RESULTS

The study comprised 17,383 new cancer cases: 11,666 in males and 5717 in females. Of these, 83% were squamous cell carcinomas. By the end of the study, 1999, the mean age at diagnosis had increased to 63 years for males and 67 for females. The age-adjusted incidence of oral and pharyngeal cancer decreased in males from 12.5 per 10(5) to 8.4 per 10(5) while it increased in females from 3.0 per 10(5) to 3.9 per 10(5). This was because of a decrease in lip cancer incidence in males, while the incidence of tongue, mouth and salivary gland cancers increased in both genders. The annual number of new oral cancer cases increased, however, in both genders.

CONCLUSION

The incidence of lip cancer decreased in males, probably because of a decrease in smoking and in outdoor work. The incidence of intra-oral cancers increased in both genders, possibly because of increased alcohol consumption.

Smokeless tobacco and health in India and South Asia

South Asia is a major producer and net exporter of tobacco. Over one-third of tobacco consumed regionally is smokeless. Traditional forms like betel quid, tobacco with lime and tobacco tooth powder are commonly used and the use of new products is increasing, not only among men but also among children, teenagers, women of reproductive age, medical and dental students and in the South Asian diaspora. Smokeless tobacco users studied prospectively in India had age-adjusted relative risks for premature mortality of 1.2-1.96 (men) and 1.3 (women). Current male chewers of betel quid with tobacco in case-control studies in India had relative risks of oral cancer varying between 1.8-5.8 and relative risks for oesophageal cancer of 2.1-3.2. Oral submucous fibrosis is increasing due to the use of processed areca nut products, many containing tobacco. Pregnant women in India who used smokeless tobacco have a threefold increased risk of stillbirth and a two- to threefold increased risk of having a low birthweight infant. In recent years, several states in India have banned the sale, manufacture and storage of gutka, a smokeless tobacco product containing areca nut. In May 2003 in India, the Tobacco Products Bill 2001 was enacted to regulate the promotion and sale of all tobacco products. In two large-scale educational interventions in India, sizable proportions of tobacco users quit during 5-10 years of follow-up and incidence rates of oral leukoplakia measured in one study fell in the intervention cohort. Tobacco education must be imparted through schools, existing government health programmes and hospital outreach programmes.

Patterns and distribution of tobacco consumption in India: cross sectional multilevel evidence from the 1998-9 national family health survey

OBJECTIVE

To investigate the demographic, socioeconomic, and geographical distribution of tobacco consumption in India.

DESIGN

Multilevel cross sectional analysis of the 1998-9 Indian national family health survey of 301 984 individuals in 92 447 households in 3215 villages in 440 districts in 26 states.

SETTING

Indian states.

PARTICIPANTS

301 984 adults (> or = 18 years).

MAIN OUTCOME MEASURES

Dichotomous variable for smoking and chewing tobacco for each respondent (1 if yes, 0 if no) as well as a combined measure of whether an individual smokes, chews tobacco, or both.

RESULTS

Smoking and chewing tobacco are systematically associated with socioeconomic markers at the individual and household level. Individuals with no education are 2.69 times more likely to smoke and chew tobacco than those with postgraduate education. Households belonging to the lowest fifth of a standard of living index were 2.54 times more likely to consume tobacco than those in the highest fifth. Scheduled tribes (odds ratio 1.23, 95% confidence interval 1.18 to 1.29) and scheduled castes (1.19, 1.16 to 1.23) were more likely to consume tobacco than other caste groups. The socioeconomic differences are more marked for smoking than for chewing tobacco. Socioeconomic markers and demographic characteristics of individuals and households do not account fully for the differences at the level of state, district, and village in smoking and chewing tobacco, with state accounting for the bulk of the variation in tobacco consumption.

CONCLUSION

The distribution of tobacco consumption is likely to maintain, and perhaps increase, the current considerable socioeconomic differentials in health in India. Interventions aimed at influencing change in tobacco consumption should consider the socioeconomic and geographical determinants of people's susceptibility to consume tobacco.

Screening programmes for the early detection and prevention of oral cancer

BACKGROUND

Although the second half of the last century has generated a rich and complex body of knowledge, the burden of oral cancer is still largely present. As with other cancers, there has been a strong debate whether screening strategies for oral cancer such as visual examination, the use of toluidine blue or newer methods such as brush biopsy or fluorescence imaging are effective in reducing the mortality rate associated with oral cancer.

OBJECTIVES

To assess the effectiveness of current screening methods in decreasing oral cancer mortality.

SEARCH STRATEGY

Electronic databases (MEDLINE, CANCERLIT, EMBASE, the Cochrane Central Register of Controlled Trials; 1966 to September 2002, The Cochrane Library - Issue 2, 2002), bibliographies, handsearching of specific journals and contact authors were used to identify published and unpublished data.

SELECTION CRITERIA

Randomised controlled trials of screening for oral cancer or potentially premalignant oral lesions using visual examination, toluidine blue, fluorescence imaging or brush biopsy.

DATA COLLECTION AND ANALYSIS

The search found 100 citations and these have been reviewed. One randomised controlled trial of screening strategies for oral cancer was identified as meeting the review's inclusion criteria. Validity assessment, data extraction and statistics evaluation have been undertaken by two independent reviewers.

MAIN RESULTS

One ongoing randomised controlled trial has been included (n = 13 clusters: 153,708 eligible subjects, 130,799 included subjects). There was no difference in the age-standardised oral cancer mortality rates for the screened group (21.2/1000,000 person years) and the control group (21.3/100,000 person years). However this study has some methodological weaknesses.

REVIEWER'S CONCLUSIONS

Given the limitation of evidence (only one included randomised controlled trial) and the potential methodological weakness in the included study, it is valid to say that there is no evidence to support or refute the use of a visual examination as a method of screening for oral cancer using a visual examination in the general population. Furthermore, no robust evidence exists to suggest other methods of screening, toluidine blue, fluorescence imaging or brush biopsy, are either beneficial or harmful. Further cost-effective, high quality studies to assess the efficacy and effectiveness of screening are required. In addition, studies to elucidate the natural history of oral cancer, prevention methods and the effectiveness of opportunistic screening in high risk groups are needed.

S-allylcysteine, a garlic constituent, inhibits 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis

The effect of S-allylcysteine (SAC), a water-soluble garlic constituent, on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis was investigated in male Syrian hamstes. Forty hamsters were divided into 4 groups of 10 animals. The right buccal pouches of the animals in Group I were painted with a 0.5% solution of DMBA in liquid paraffin three times a week. The animals in Group II were painted with DMBA as in Group I and, in addition, received 200 mg/kg body wt p.o. SAC three times a week on days alternate to DMBA application. Group III animals received SAC as in Group II. Group IV animals received neither DMBA nor SAC and served as the control. The hamsters were killed after an experimental period of 14 wk. Measurement of lipid peroxidation, the antioxidant enzymes superoxide dismutase (SOD) and catalase, in the buccal pouch mucosa, liver, and circulation was used to monitor the chemopreventive potential of SAC. All hamsters painted with DMBA alone developed tumors identified histologically as well-differentiated squamous cell carcinomas. In hamsters bearing DMBA-induced buccal pouch tumors, diminished lipid peroxidation in the tumor tissue was accompanied by decreased activities of SOD and catalase, whereas in the liver and circulation, enhanced lipid peroxidation was associated with compromised antioxidant defenses. Administration of SAC suppressed the incidence of DMBA-induced HBP tumors as revealed by the absence of carcinomas. Histologically, only keratosis was observed. SAC modulated DMBA-induced decreased susceptibility of the HBP to lipid peroxidation while simultaneously enhancing SOD and catalase activities, whereas in the liver and circulation, SAC decreased the extent of lipid peroxidation and significantly enhanced antioxidant activities. We suggest that SAC exerts its chemopreventive effects by modulating lipid peroxidation and enhancing antioxidant activities in the target organ as well as in the liver and circulation.

Oxidant-antioxidant status in patients with oral squamous cell carcinomas at different intraoral sites

OBJECTIVES

To compare the extent of lipid peroxidation and the status of antioxidants in tumor and venous blood of patients with oral squamous cell carcinoma (OSCC) at different intraoral sites.

DESIGN AND METHODS

Twenty four patients with OSCC at different intraoral sites and an equal number of age- and sex-matched reference subjects were chosen for the study. The concentrations of lipid peroxides and reduced glutathione (GSH) and the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were estimated in tissues and blood.

RESULTS

Diminished lipid peroxidation in tumor tissue was accompanied by decreased activities of SOD and CAT with increase in GSH and GSH-dependent enzymes. In contrast, enhanced lipid peroxidation with decrease in antioxidants was observed in the venous blood of OSCC patients.

CONCLUSION

No significant differences in lipid peroxidation and antioxidant levels were observed between patients with OSCC at different intraoral sites. However, our results revealed differences between the tumor and blood with respect to their susceptibility to lipid peroxidation and antioxidant status.

5.1 The demography of oral diseases, future challenges and the implications for dental education

This Section considered the immense challenges presented by the changing demography of populations (in particular, cross-boundary flow), changing oral and dental disease trends. It also considered the difficulties of gathering data on such information. It then considered how these challenges may affect the education of the dental team in the future. The Section considered the concept of the 'global village' as a representation of the changing world demography. We were at pains to recognize that our role was in considering both emerging and established market economies. In fact, a major part of the Section's activities concentrated on the development of the professional ethic of social responsibility - represented at the local, regional, national and international levels. We considered a finite group of oral and dental diseases, namely dental caries, periodontal diseases, oral cancer and cranio-facial disorders. In addition, we chose to comment on systemic diseases influenced by oral diseases, oral diseases influenced by systemic diseases and iatrogenic diseases (including prion disorders and cross-infection control issues). The Section recognized the profound difference between needs and demands in the provision of oral and dental health care. We considered the concept of best practices within our working remit and named these as: * the gathering of valid data on health trends; * uniformity in the measurement of disease and diagnostic parameters; * the identification of a core curriculum which best addresses an increased awareness of changing demography; and * a multidisciplinary approach to education and research in the context of global collaboration. The Section recognized the enormous potential for global networking with the explosion of information and communication technology. We investigated the requirements in converging towards higher global standards, while accepting and appreciating important regional and continental differences. To this end, the Section has put forward a number of important recommendations and realistic goals.

Expression of bcl-2 and bax in chewing tobacco-induced oral cancers and oral lesions from India

Deregulation of oncogenes and tumor suppressor genes involved in apoptosis has been associated with tumor development and progression. To investigate the involvement of apoptosis regulating proteins in oral cancer in Indian patients, primarily associated with chewing tobacco habits, immunohistochemical expression of bcl-2 and bax was examined in 63 oral squamous cell carcinomas, and 31 putative premalignant lesions. Our studies revealed overexpression of tumor specific cytoplasmic bcl-2 in 56% and bax in 43% oral cancers. The oral cancers in the Indian patients are preceded by premalignant oral lesions; hence oral lesions were examined for bcl-2 and bax expression. We observed aberrant expression of bcl-2 in 16% oral lesions comprising leukoplakias and SMF and bax in 55% oral lesions. We have already reported, p53 expression in these oral cancers and lesions. It was noteworthy that 30% oral cancers demonstrated a p53+bcl2+ pattern, and 14% samples exhibited p53+bcl2+bax+ pattern. However, none of the oral lesions showed concurrent deregulation of p53 and bcl-2 or all the three genes. Interestingly 45% oral lesions were p53-bax+ as compared to 18% oral cancers; while 39% oral lesions were bcl2-bax+ as compared to 14% oral cancers, indicating overexpression of bax in oral lesions, in the absence of p53 and bcl-2 proteins. Significant correlation was observed between positive nodal status and bcl2+ (p=0.047) and p53+bcl-2+ (p=0.01) in oral cancers. Kaplan Meier survival analysis showed significantly (p=0.059) higher survival in patients with p53- oral tumors than with p53+ tumors. Our studies thus indicate frequent overexpression of apoptosis regulators bcl-2, bax and p53 proteins in oral cancers, and a subset of oral lesions, representing early events in oral car-cinogenesis. The aberrant bcl-2 expression and loss of p53 function observed, may play an important role in the tumorigenesis of oral cancers by allowing escape from apoptosis and enabling additional genetic alterations to accrue.

Expression of RARalpha and RARbeta in human oral potentially malignant and neoplastic lesions

Retinoids reverse potentially malignant lesions and inhibit the development of second primary cancers in patients with head-and-neck cancer. Many of the effects of retinoids result from modulation of gene expression by 2 distinct classes of nuclear receptor, RARs and RXRs; alterations in their expression can lead to tumorigenesis. To determine whether aberrations in expression of the receptors are related to the development of betel- and tobacco-related oral cancer, we used specific monoclonal antibodies against RARalpha and RARbeta to detect expression of these proteins in 30 histopathologically normal tissues, 45 potentially malignant lesions (leukoplakia) with histological evidence of either hyperplasia (31 cases) or dysplasia (14 cases) and 64 oral squamous-cell carcinomas (SCCs) by immunohistochemistry. Of the 30 normal oral tissues analysed, 8 cases showed detectable levels of RARalpha protein, while 10 cases did not show detectable RARbeta immunoreactivity. Immunostaining for RARalpha protein was observed in 12/31 (39%) hyperplastic lesions, 6/14 (43%) dysplastic lesions and 43/64 (67%) oral SCCs. Expression of RARalpha in oral SCC was significantly associated with the histological differentiation status of tumours (p = 0.016). In contrast, lack of detectable immunoreactivity was observed in 19/31 (61%) hyperplastic lesions, 8/14 (57%) dysplastic lesions and 21/64 (33%) oral SCCs. The hallmark of the study was the significant increase in RARalpha immunopositivity in oral SCCs compared to normal tissue (p = 0.0005) and hyperplastic lesions (p = 0.016). One intriguing feature was the significant decrease in RARbeta immunopositivity in hyperplastic lesions compared with normal oral mucosa (p = 0.05) as well as in oral SCCs compared with normal tissues (p = 0.0008).