Remission of oral leukoplakias and micronuclei in tobacco/betel quid chewers treated with beta-carotene and with beta-carotene plus vitamin A

Chemoprevention of head and neck cancer

Increasing emphasis has been placed on chemo-prevention as understanding of the genetic and molecular events of carcinogenesis has evolved. More than 1000 compounds that inhibit cancer development in vitro or in animal models have been identified, and active research is under way to determine which of these agents will be both effective and nontoxic in human beings. Currently, 13-cis-retinoic acid is the most studied chemopreventive agent against head and neck cancers. Unfortunately, this vitamin A derivative has significant clinical toxicity, which limits its utility in a practice setting. The efficacy of the retinoids, however, has stimulated efforts to find other chemopreventive compounds that are both effective and non-toxic. This review discusses head and neck premalignancy, chemoprevention strategies, retinoids, and several other classes of chemopreventive agents with potential efficacy against head and neck premalignancy.

Biomarkers and molecular epidemiology and chemoprevention of oral carcinogenesis

Chemopreventives are chemicals that prevent the formation of cancers such as oral cancer. They can take the form of nutrients or synthetic molecules, and their fundamental characteristic is that they do not produce disease processes that would result in debilitating symptoms. Current evidence indicates that they function by modifying the oxidative state of transforming cells. Biomarkers can take the form of genetic and molecular indicators, which characterize the function of chemopreventives and cancer processes such as oral carcinogenesis. Biomarkers cannot provide all the required information for risk assessment or possible activity of the chemopreventives. Other methods, such as epidemiological analyses and techniques, must be used to enhance our understanding of the risk for oral cancer in human populations. One common epidemiologic method, the questionnaire, helps to determine the use and carcinogenic potential of tobacco and alcohol during oral carcinogenesis. Genetic and molecular changes in human patient populations may result in a reduction in the number and function of tumor suppressor genes. If these changes are to be assessed, the tissues (e.g., buccal mucosa) must be accessible and harvested in a reliable and consistent manner for the acquisition of DNA, mRNA, and protein. Oral tissues provide sufficient quantities of these molecules and, under stringent conditions, the quality required for the isolation of these molecular constituents. In conjunction with epidemiologic techniques, various genotypic polymorphisms, such as glutathione-S-transferase (GSTM1) or cytochrome P450 (CYP450A1), have indicated a loss in carcinogen detoxification or the processing of internal growth control signals. Biomarkers are composed of a large diverse group of genetic and molecular structures. Some of these biomarkers are indicators for programmed cell death (PCD), while others describe malignant tumor growth. Many of these classes of molecules are oxidative-responsive (e.g., tumor suppressor p53, Bcl-2, growth factors, immune-derived proteins, and death-inducing molecules) and induce PCD by triggering a cascade of cysteine proteases and regulators (e.g., caspases, death receptors). This pathway results in cell-cycle alterations and DNA fragmentation. It is hoped that a detailed knowledge of the processes involved in malignant transformation will better define the biomarker-screening tools for oral cancer. These tools will enhance our ability to predict the incidence of cancer, detect early malignant change, and quantitate chemoprevention during oral carcinogenesis. Chemopreventives such as the retinoids have already demonstrated their ability to suppress potential malignant changes in pre-malignant oral leukoplakias and decrease the incidence of second head-and-neck cancer primaries. It is our hope that this review will increase investigators' interest in developing new screening and detection systems for oral cancer.

Chemoprevention with interferon alfa and 13-cis retinoic acid in the adjunctive treatment of head and neck cancer

BACKGROUND

Retinoids have been increasingly used since the mid-1960s for the treatment of leukoplakia and dysplasia of the head and neck. Studies of their use in the treatment of carcinomas of the head and neck, usually in combination with interferons, have also been published in recent years.

METHODS

30 patients (25 men, five women) with UICC stage IV were given adjunctive treatment with a combination of 3 x 3 million IU of interferon alfa SC weekly and 0.5 mg/kg body weight of 13-cis retinoic acid PO daily for a maximum duration of 6 months. The therapeutic benefits and side effects are reported here.

RESULTS

Therapy was completed as scheduled in 16 out of 30 patients. Reasons for stopping treatment: progressive disease (ten patients), side effects (four patients). 18 patients were tumor-free following treatment. 16 patients displayed a complete response one year after completion of adjunctive treatment. Retinoic-associated side effects observed included xerostomia (90%), dysphagia (67%), weight loss (50%), flush (50%) and cachexia (7%). Interferon-associated side effects included pyrexia and moderate hematological changes.

CONCLUSION

Adjunctive combination treatment with interferon alfa and 13-cis retinoic acid appears to be beneficial to patients with head and neck cancer. The side effects are moderate.

Beta - caroteno e câncer

Há mais de vinte anos tem-se pesquisado sobre a relação entre β-caroteno e câncer. Inúmeros trabalhos têm tentado esclarecer a hipótese, formulada a partir de achados epidemiológicos e experimentais, de que o carotenóide poderia agir como anticarcinogênico de origem alimentar. Estudos epidemiológicos observacionais, tipo caso-controle e coorte, sugerem que o consumo elevado de frutas e vegetais ricos em β-caroteno reduz o risco de câncer, especialmente de pulmão. Estudos de intervenção em humanos, administrando doses farmacológicas crônicas a milhares de indivíduos, têm demonstrado resultados contraditórios. Pesquisas em animais experimentais e em cultura de células apontam o carotenóide como quimiopreventivo, agindo sobretudo como retinóides, através de conversão metabólica extra-intestinal e como antioxidante de membrana. Conclui-se que o β-caroteno pode proteger contra o câncer, quando suplementado em doses fisiológicas, isto é, cerca de 4 a 6mg/dia. Doses farmacológicas crônicas não estão recomendadas para indivíduos saudáveis e particularmente para tabagistas.

Chromosomal damage rate, aging, and diet

Chromosomal damage as measured by frequency of translocations, acentric fragments, telomere shortening, nondisjunction, chromosome loss, aneuploidy, and micronucleus formation has been shown to increase progressively with age. Using the cytokinesis-block micronucleus technique, which provides an efficient measure of chromosomal breakage and loss, we have been able to show that aging can explain at least 25% of the variation in chromosomal damage rate in lymphocytes from both males and females. We have also performed cross-sectional and placebo-controlled intervention studies to determine the relationship between the micronucleus (MN) frequency in lymphocytes and diet, and blood status for vitamins C, E, B12, and folic acid. Our studies have shown that MN frequency in the 41- to 60-year age group is significantly lower in vegetarians when compared to nonvegetarians, but the reverse was true in males aged between 20 and 40 years. This was accounted for by a deficient/low B12 status in vegetarian males; there was no difference in the MN frequency of vegetarian and nonvegetarian subjects aged between 61 and 90 years. Results from this study also showed significant negative correlations of MN frequency with folic acid and vitamin B12 but not with vitamin C or vitamin E. In separate studies on healthy men aged 50-70, we have verified the significant negative correlation between vitamin B12 status in plasma and MN frequency (r = -0.315, p = 0.013) in subjects who were not vitamin B12 deficient and observed a significant positive correlation between MN frequency and homocysteine status (r = 0.414, p = 0.0086) in those men who were not vitamin B12 and/or folate deficient. These data suggest that MN frequency is minimized when plasma B12 is above 300 pmol/L and plasma homocysteine is below 7.5 mumol/L. Double-blind placebo-controlled intervention studies conducted over four months have shown that above RDI intake of vitamin E (30 x RDI) or folic acid (10 x RDI) did not produce a significant reduction in MN frequency in men aged 50-70 years. In the latter case plasma homocysteine was reduced from a mean value of 9.33 mumol/L to 8.51 mumol/L, a level that does not correspond with minimization of MN frequency. We have also tested the hypothesis that moderate wine drinking can protect against the DNA-damaging effect of hydrogen peroxide and found that there was a strong ex vivo inhibition (> 70%) of hydrogen peroxide-induced MN frequency by plasma samples from blood collected one hour after consumption of red or white wine, as compared to plasma samples collected immediately before wine consumption (p = 0.0008). However, only samples following red wine consumption produced a significant reduction in baseline MN frequency. The above results suggest that chromosome damage can be modulated, under selected circumstances, by diverse dietary factors.

Oral cancer in the UK: to screen or not to screen

Although oral squamous cell carcinoma accounts for only a small proportion of malignant neoplasms in the UK, oral cancer incidence and mortality rates have been rising in recent years. The natural history of oral cancer is not adequately understood at present and there is very little information about the epidemiology of precancerous lesions in the UK. There are also insufficient data to provide firm evidence that the percentage of cases arising de novo is greater in the UK and the Western world as compared to the Indian subcontinent. Screening for oral cancer by visual examination is simple, inexpensive and causes little discomfort; however, there is no evidence for the effectiveness of screening for oral cancer either in reducing mortality from the disease or in reducing the incidence of invasive disease by detection and treatment of precancerous lesions. There is currently insufficient evidence to recommend population screening for oral cancer in the UK. Measures aimed at primary prevention of the disease may be a more feasible method of disease control at present.

Micronuclei in lymphocytes and exfoliated buccal cells of postmenopausal women with dietary changes in folate

Folate deficiency is associated with anemia, birth defects, cancer and neuropsychiatric disorders. The purpose of this study was to determine if a moderate folate deficiency during controlled changes in folate intake would affect chromosomal damage in lymphocytes and buccal cells. A study of nine healthy postmenopausal women volunteers (age 49-63 years) was carried out in a metabolic unit (baseline week with folate intake of 195 microg/day, five-week depletion at 56 microg/day, and gradual repletion including four weeks at 111 microg/day, 11 days at 286 microg/day and 9 days at 516 microg/day). Plasma folate, vitamin B-12, and homocysteine were measured weekly. Cytogenetic damage was assessed by scoring micronucleus (MN) frequency in lymphocytes and buccal cells three times: (1) at the beginning of the study, (2) at the end of depletion, and (3) after repletion. The MN frequency increased in binucleated lymphocytes, as well as in all lymphocytes, after depletion (p=0.037), and later decreased following repletion (p=0. 028). Both kinetochore-positive and kinetochore-negative MN were increased after depletion (p=0.015 and 0.028), but after repletion only the change in kinetochore-positive MN was statistically significant (p=0.048). The main variables affecting MN were: (1) vitamin B-12 level, (2) plasma folate level, and (3) baseline frequency of MN. The MN frequency in exfoliated buccal cells was decreased after dietary supplementation of 516 microg/day folate (p=0.010). Thus, low folate, without clinical symptoms of anemia, results in higher levels of cytogenetic damage in both the blood and oral cavity of postmenopausal women.

Topical bleomycin for the treatment of dysplastic oral leukoplakia

BACKGROUND

Because malignant transformation of dysplastic oral leukoplakia has been reported in up to 43% of cases, these lesions must be managed.

METHODS

This study evaluated the use of topical 1% bleomycin in dimethylsulfoxide for the treatment of dysplastic oral lesions. Bleomycin was applied once daily for 14 consecutive days to lesions of the oral mucosa in 19 patients. Immediate posttreatment biopsies and the clinical response were evaluated and clinical follow-up was conducted for as long as possible.

RESULTS

The mean age of the patients at diagnosis was 59.4 years and 74% were tobacco users. Seventy-five percent of patients had resolution of dysplasia at follow-up biopsy, with a mean improvement of two histologic grades of dysplasia after topical chemotherapy. Ninety-four percent of the patients attained at least partial responses. After a mean follow-up period of 3.4 years, 31.6% of patients had no clinically visible lesions and 47.4% of patients had clinically benign lesions of homogeneous leukoplakia or minimal visible leukoplakia. In 2 patients (11%) malignant transformation occurred a mean of 1.75 years after bleomycin treatment.

CONCLUSIONS

Topical bleomycin may prevent the potential progression of leukoplakia through dysplasia to carcinoma. Close follow-up of all patients with dysplasia is required.

Chemoprevention of lung cancer: the rise and demise of beta-carotene

Beta-carotene and retinoids were the most promising agents against common cancers when the National Cancer Institute mounted a substantial program of population-based trials in the early 1980s. Both major lung cancer chemoprevention trials not only showed no benefit, but had significant increases in lung cancer incidence and in cardiovascular and total mortality. A new generation of laboratory research has been stimulated. Rational public health recommendations at this time include: 1. Five-A-Day servings of fruits and vegetables, a doubling of current mean intake; 2. systematic investigation of the covariates of extremes of fruit and vegetable intake; 3. discouragement of beta-carotene supplement use, due to adverse effects in smokers and no evidence of benefit in non-smokers; 4. multilevel research to develop and evaluate candidate chemoprevention agents to prevent lung and other common cancers; and 5. continued priority for smoking prevention, smoking cessation, and avoidance of known carcinogens in the environment.

The potential role of antioxidant vitamins in preventing cardiovascular diseases and cancers

Cardiovascular diseases and cancers constitute major public health problems in all industrialized countries, where they are the main causes of premature mortality. There is a large body of evidence suggesting that free-radical production can directly or indirectly play a major role in cellular processes implicated in atherosclerosis and carcinogenesis. Here we present mechanistic data and results of epidemiologic studies on the relationship between antioxidant vitamin intake or biochemical status and the risk of cancer and cardiovascular diseases. Most epidemiologic data obtained on this topic were based on an observational approach, i.e., ecologic, case-control, or prospective studies. All these studies indicate that a high dietary intake or high blood concentrations of antioxidant vitamins are associated with a reduced risk of cardiovascular diseases and cancer at several common sites. Although the results of these studies are convergent, they merely suggest a relationship at the population and individual level but do not affirm a causality link. Only intervention studies (randomized trials), by specifically changing antioxidant vitamin intake, can provide conclusive answers. The apparent discrepancies between the results of four recently published trials may be explained by the type of population (general or high-risk subjects), the differing doses of supplementation (nutritional levels or higher), the number of antioxidants tested (one, two, or more), and the type of administration (alone or in balanced association). It thus appears that a low risk of pathologies may be related to multiple nutrients consumed at nutritional doses and in combination. Optimal effects may be expected with a combination of nutrients at levels similar to those found in a healthy diet. A single antioxidant vitamin given at high doses in subjects with high risk of pathologies (smokers, asbestos-exposed subjects) may not have substantial benefits and could even have negative consequences.

Diet, nutrients, and gastrointestinal cancer

Tobacco and alcohol use are strong risk factors for cancer of the upper gastrointestinal tract. Saturated fat and red meat intake also appear to increase the risk of colorectal cancer. The strongest and most consistent dietary protective factors for gastrointestinal cancer are vegetables and fruits. Some micronutrients show beneficial effects, but the degree of protection is less than that observed from whole plant foods. Substantial decreases in the morbidity and mortality from gastrointestinal cancer could occur with more widespread adoption of dietary guidelines designed for cancer prevention.

Long-term supplementation with alpha-tocopherol and beta-carotene and prevalence of oral mucosal lesions in smokers

OBJECTIVE

To assess the effect of alpha-tocopherol and beta-carotene supplementation on the prevalence of oral mucosal lesions in smokers.

DESIGN

An end-point examination of a random sample of participants in a controlled trial for 5-7 years (Alpha-Tocopherol Beta-Carotene Cancer Prevention Study) in Helsinki, Finland.

SUBJECTS

A total of 409 white male cigarette smokers, aged 55-74 years who received either alpha-tocopherol (50 mg per day) or beta-carotene (20 mg per day) supplementation, both of these or placebo capsules.

METHODS

Clinical examination of oral mucosae, histological examination of lesions showing leukoplakia and cytological examination of buccal epithelium. Statistical analysis using Fisher's exact test.

RESULTS

No statistically significant differences were found between the study groups either in the prevalence of oral mucosal lesions or in the cells of unkeratinized epithelium. Leukoplakia was present in 24 (5.9%) of the subjects. Seven lesions showed dysplasia.

CONCLUSION

The present study on oral health does not support the hypothesis that alpha-tocopherol or beta-carotene supplementation plays an essential role in preventing oral mucosal changes in smokers.

Cancer chemoprevention. A new way to treat cancer before it happens

Cancer chemoprevention uses noncytotoxic drugs or nutrients to prevent, retard, or delay carcinogenesis. The future of cancer chemoprevention depends on understanding key cellular growth and proliferation-controlling events, developing markers of molecular carcinogenesis, surrogate endpoint biomarkers, and targeted chemopreventive approaches.

Lycopene: chemistry, biology, and implications for human health and disease

A diet rich in carotenoid-containing foods is associated with a number of health benefits. Lycopene provides the familiar red color to tomato products and is one of the major carotenoids in the diet of North Americans and Europeans. Interest in lycopene is growing rapidly following the recent publication of epidemiologic studies implicating lycopene in the prevention of cardiovascular disease and cancers of the prostate or gastrointestinal tract. Lycopene has unique structural and chemical features that may contribute to specific biological properties. Data concerning lycopene bioavailability, tissue distribution, metabolism, excretion, and biological actions in experimental animals and humans are beginning to accumulate although much additional research is necessary. This review will summarize our knowledge in these areas as well as the associations between lycopene consumption and human health.

Chemoprevention of oral leukoplakia with vitamin A and beta carotene: an assessment

We conducted a double-blind placebo-controlled trial to evaluate the chemopreventive potential of either vitamin A alone or beta carotene alone in subjects with oral leukoplakia in Kerala, India. We randomised 160 fishermen and women with oral precancerous lesions to receive oral vitamin A (retinyl acetate 300,000 IU/week x 12 months, n = 50), or beta carotene (360 mg/week x 12 months, n = 55), or placebo (n = 55). Blood, saliva and urine samples were collected at baseline and at exit to study serum micronutrients and mutagenicity assays. Biopsies of the mucosal lesions at entry were performed for histopathological exclusion of malignancy. The subjects were examined once every 2 months to establish clinical response of lesions and toxicity, if any. The results are based on 43 complaint subjects on placebo, 42 on vitamin A and 46 on beta carotene. The complete regression rates were: 10% in the placebo arm, 52% with vitamin A and 33% with beta carotene (P < 0.0001). Homogeneous leukoplakias and smaller lesions responded better than non-homogeneous and larger lesions. No major toxicities were observed. Half of the responders with beta carotene and two thirds with vitamin A relapsed after stopping supplementation. Serum beta carotene concentration increased substantially with beta carotene administration while with vitamin A supplementation there was no change in serum retinol levels. In the vitamin A treated group there was a significant decrease in serum alpha tocopherol. Vitamin A administration resulted in a significant remission of oral leukoplakia without any side effects of prolonged vitamin A supplementation. The results of this study, as well as those from previous studies, appear to provide strong supporting evidence to justify long term trials with vitamin A in subjects with high-risk leukoplakias with oral cancer as an endpoint.

The utility of toluidine blue application as a diagnostic aid in patients previously treated for upper oropharyngeal carcinoma

OBJECTIVES

This study evaluated the utility (usefulness) of toluidine blue application as an aid to the recognition and diagnosis of clinically evident lesions in a series of patients previously treated for oral cancer and monitored in a cancer center. In addition to increased risk of recurrence of cancer or new second primary lesions, patients who have had previous treatment for oropharyngeal cancer may be more difficult to assess because of tissue changes that occur as a result of previous radiation therapy.

STUDY DESIGN

Patients with a history of oral malignancy were assessed by clinical examination followed by application of toluidine blue. Biopsy sites were determined on the basis of unaided visual examination and by the findings on toluidine blue application. Biopsy specimens were reviewed by a pathologist blinded to the clinical findings.

RESULTS

Unaided clinical examination identified 78% of carcinoma in situ or invasive malignant lesions compared with toluidine blue application, which identified all (100%) carcinoma in situ or invasive malignant lesions (p = 0.02) and produced no false-negative findings. No differences were found between clinical examination and toluidine application in the detection of dysplastic lesions.

CONCLUSION

Toluidine blue retention was seen in all cases of carcinoma in situ and invasive carcinoma, and no false-negative findings were seen with toluidine blue. When used by a trained and experienced clinician in a cancer center, toluidine blue was a valuable visual aid to clinical examination of oral mucosal lesions.

Head and Neck Chemoprevention: Recent Advances

BACKGROUND: Head and neck cancers are important to human life and health in both developed and underdeveloped countries. Management of established cancers is difficult, and there is great interest in evaluating methods to prevent these tumors from developing. METHODS: The biology of carcinogenesis, including field carcinogenesis, is reviewed, together with the biology and pharmacology of the retinoids. Intervention studies of premalignant lesions have led to prospective clinical trials of the capability of various retinoids to reduce the incidence of new second cancers. RESULTS: High-dose 13-cis-retinoic acid (13cRA) has significant activity in reversing oral leukoplakia but at a cost of substantial toxicity, and relapses occur early. An ongoing intergroup trial is underway to evaluate the capacity of low-dose (30 mg/d) 13cRA given for three years to reduce the incidence of second primary tumors in patients with "cured" squamous head and neck cancers. CONCLUSIONS: Molecular studies of loss of heterozygosity and p53 gene mutations are advancing our understanding of field carcinogenesis and the biology, pharmacology, and effects of the retinoids used in cancer prevention. Translation of early clinical trials into large-scale intervention trials to prevent second cancers are now underway.

Molecular epidemiology and retinoid chemoprevention of head and neck cancer

Head and neck cancer is a major worldwide health problem; it has been estimated that approximately 900,000 people were diagnosed with this disease in 1995. Patients are generally treated with surgery and/or radiation therapy. Treatment, especially of patients with early stage (I or II) head and neck squamous cell carcinoma, is often successful. A serious concern, however, is the fact that these patients subsequently develop second primary tumors at an annual rate of 4%-7%. Molecular analyses of premalignant and malignant tissues have produced strong evidence that clonal genetic alterations occur during the early stage of aerodigestive tract carcinogenesis. Although the roles of tobacco and diet in head and neck carcinogenesis have been the subjects of epidemiologic investigations for many years, it has only recently become possible to integrate information regarding genetic susceptibility factors into the development of comprehensive risk models for these cancers. The molecular and epidemiologic studies provide the foundation on which clinical trials can be designed to evaluate the role of retinoids and other compounds in the reversal of premalignancy and the prevention of second primary tumors (i.e., in chemoprevention). This translational approach has led to studies of the utility of intermediate end point markers, such as the nuclear retinoic acid receptors, in chemoprevention strategies. Given the rapid advances occurring in this area of research, it may soon be possible to use these biomarkers to identify patients who are most at risk for developing head and neck cancer and who are most likely to benefit from chemopreventive interventions.

Positive impact of retinyl palmitate in leukoplakia of the larynx

Laryngeal leukoplakia can be a premalignant precursor of squamous cell carcinoma, is often tobacco-related and can usually be readily monitored by indirect laryngoscopy. One of the main motivations for using retinyl palmitate in patients with persistent leukoplakia was to avoid general anesthesia for elderly patients, who are considered to be high-risk patients when direct larynoscopy is required for possible tissue biopsy. Our study was the first to investigate the effectiveness and toxicity of high-dose retinyl palmitate in the treatment of laryngeal leukoplakia. Treatment was divided into two phases. In the first phase, all patients underwent induction therapy with 300,000 IU/day of retinyl palmitate for the 1st week, which was then adjusted up to 1,500,000 IU/day in the 5th week in patients with resistant lesions. Patients whose lesions progressed during this period were withdrawn from the study. In the second phase, patients whose lesions responded to treatment or remained stable were assigned to a maintenance therapy of 150,000 IU/day. Complete remission was observed in 15 of 20 patients (75% of cases). Partial response was seen in the remaining 5 patients, with 3 of the patients relapsing. The median duration of treatment and follow-up was 18 months (range, 12-24 months). These results indicate that retinyl palmitate has substantial activity in laryngeal leukoplakias. Since only minor side effects were seen, the medication is an excellent candidate as a preventive agent for laryngeal cancer.

Evaluation of multiple micronutrient supplementation in the management of oral submucous fibrosis in Karachi, Pakistan

Oral submucous fibrosis (OSF) is an oral precancerous condition characterized by symptoms such as intolerance to spicy food, altered salivation, progressive difficulty in opening the mouth, and signs like vesiculation, ulceration, blanching, rigidity, and stiffening of the oral mucosa and depapillation and altered mobility of the tongue. It is seen mostly among people of Indian subcontinent origin. The major structural change is extensive fibroelastic scarring of the lamina propria and deeper connective tissues. A combination of micronutrients (vitamins A, B complex, C, D, and E) and minerals (iron, calcium, copper, zinc, magnesium, and others) was evaluated for its efficacy in controlling the symptoms and signs of OSF in 117 compliant subjects in Karachi, Pakistan, in a single-arm preliminary study. The subjects received supplementation for one to three years. Significant improvement in symptoms, notably intolerance to spicy food, burning sensation, and mouth opening, was observed at exit. The interincisor distance deteriorated in 11 subjects (10%) at exit; it was stable in 56 subjects (49%) and improved in 48 (41%). The mean interincisor distance was 19.1 +/- 10.8 (SD) mm at exit compared with 16.2 +/- 7.5 mm at baseline. A significant proportion of concomitant lesions like leukoplakia also regressed at exit. The major outcome from this study was a beneficial clinical response in subjects with OSF to multiple micronutrient intervention, which justifies its further evaluation in well-designed randomized controlled trials in other settings in South Asia.

Serial cytological assay of micronucleus induction: a new tool to predict human cancer radiosensitivity

BACKGROUND AND PURPOSE

The micronucleus test, generally done in cultured tumour cells irradiated in vitro, has not gained wide acceptance in predicting human cancer radiosensitivity. The purpose of this study was to see if micronucleus assay by serial scrape smear cytology can predict oral cancer radiosensitivity.

MATERIALS AND METHODS

Forty nine oral cancer patients given radiotherapy (60 Gy/25 fractions/5 weeks) form the study population. Serial scrape smears were taken from their tumours before treatment and after delivery of 2, 5, 8 and 12 fractions, stained by Giemsa and the number of micronucleated cells (MNC) noted. The patients were grouped to those who developed tumour recurrence ('Resistant') and those who did not ('Sensitive'), and the pattern of micronucleus induction compared.

RESULTS

Both groups of tumours had MNC even before treatment, with statistically significant dose-related increase with radiotherapy. The sensitive group had a higher mean increase in MNC count than the resistant group (6.1 times and 3.6 times the pre-treatment value, respectively) and better correlation with dose (r = 0.54 vs. 0.43). The increase in MNC count occurred earlier in the resistant group than in the sensitive, the TMNC (time for the pre-treatment value to double) being 3.3 days and 7.6 days, respectively. Also, the resistant group showed a plateauing of the MNC count which the sensitive group lacked.

CONCLUSIONS

The higher MNC induction in the sensitive tumours suggests the usefulness of the assay as a test of radiosensitivity. The differing patterns of MNC increase suggest that differences in proliferation rate is an important cause of tumour failure. Serial cytological assay of micronucleus induction can identify both radiosensitivity and proliferation characteristics of tumours, and thus may turn out to be a useful test of radiocurability.

Long-term follow-up of larynx leukoplakia under treatment with retinyl palmitate

BACKGROUND

Larynx leukoplakia can be a premalignant precursor of squamous cell carcinoma, is often tobacco related, and can be monitored easily by indirect laryngoscopy. One of the main motivations for using retinyl palmitate in patients with larynx leukoplakia was to avoid general anesthesia for the elderly patients, who are considered to be at high risk for undergoing direct laryngoscopy. Our study investigates for the first time the effectiveness and toxicity of high-dose retinyl palmitate in the treatment of larynx leukoplakia.

METHODS

Treatment was divided into two phases. In the first phase, all patients underwent induction therapy with a high-dose of retinyl palmitate (A-Mulsin Hochkonzentrat, Mucos Pharma, Geretsried, Germany) with 300,000 IU/day for the first week and up to 1,500,000 IU/day, in patients with resistant lesions, in the fifth week. Patients whose lesions progressed during this period were withdrawn from the study. In the second phase, patients whose lesions responded to treatment or remained stable were then assigned to a maintenance therapy of 150,000 IU/day.

RESULTS

We observed a complete remission rate of 75% (15 of 20 patients). Among the 5 patients with partial response, 3 relapsed. The median duration of treatment and follow up was 18 months (range 12-24 months).

CONCLUSIONS

These results indicate that retinyl palmitate has substantial activity in larynx leukoplakias. Furthermore, only minor side effects make it an excellent candidate as a preventive agent for larynx cancer.

Radioprotection of beta-carotene evaluated on mouse somatic and germ cells

In the present paper, the protective effect of beta-carotene was evaluated after whole body exposure of mice to 2 Gy of X-rays. Splenocytes, reticulocytes, bone marrow cells and spermatids were evaluated for the frequency of micronuclei (MN) induced by X-rays. Mice were treated (gavage) with beta-carotene (10, 25 and 50 mg/kg b.w.) for 5 consecutive days and, 4 h after the last treatment, the animals were irradiated. The results obtained showed different frequencies of X-ray-induced-MN between different cell populations analysed and also different response of these cells to the beta-carotene treatment. The radioprotective effect of beta-carotene was observed in splenocytes, reticulocytes, and spermatids but not in bone marrow cells. No dose-response relationship for beta-carotene was detected. The time of sampling, the sensitivity of the cells as well as the antioxidant activity of beta-carotene are discussed as important factors for the radioprotective action of this provitamin.

Hexamethylene bisacetamide as a chemopreventive agent in hamster cheek pouch tumorigenesis

The chemopreventive effect of oral and intraperitoneal (i.p.) administration of hexamethylene bisacetamide (HMBA) on 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced tumour formation in hamster cheek pouches was investigated. Male Syrian hamsters were treated by painting both cheek pouches with a 0.5% solution of DMBA twice weekly for 11 weeks. In addition to DMBA application, Group 1 hamsters were given 1% HMBA continuously in the drinking water and Group 2 hamsters received i.p. injection of HMBA at a dose of 500 mg/kg three times per week during the experiment. Group 3 animals received DMBA application alone. Thirteen weeks after the start of the experiment, the numbers of cheek pouch tumours and tumour volume were significantly decreased by oral but not i.p. administration of HMBA. Low levels of HMBA were detected in the plasma of the hamsters which were given 1% HMBA in drinking water. These results indicate that oral administration of HMBA can act as a chemopreventive agent against hamster cheek pouch tumorigenesis.

Influence of benzylisothiocyanate and 13-cis-retinoic acid on micronucleus formation induced by benzo[a]pyrene

The purpose of this study was to investigate the influence of benzylisothiocyanate (BIT) and 13-cis-retinoic acid (RA) upon the genotoxic potential of benzo[a]pyrene (BaP) to induce micronucleus formation in the bone marrow of mice. Eighty-two male mice were divided into 10 groups. One group served as a negative control (olive oil intubation). Four groups received an oral intubation of various concentrations of BIT (15 to 120 mg/kg) and i.p. injections of BaP (185 mg/kg). Another four groups were treated identically, but received RA (20 to 150 mg/kg) in place of BIT. Finally, one group received only i.p. injection of BaP (185 mg/kg). The results showed that both BIT and RA significantly reduced the frequency of micronucleus formation in the bone marrow of the BaP treated animals. BIT was found to be effective at all the tested concentrations. RA was effective only at three of the four tested concentrations (40, 75 and 150 mg/kg). These findings indicate that both BIT and RA may reduce the genotoxic effects of benzo[a]pyrene in the mice under the test conditions utilized.

Molecular changes in oral cancer may reflect aetiology and ethnic origin

Oral cancer, although uncommon in the Western world, accounts for up to 40% of all malignancies in parts of India and South East Asia. Recognised aetiological agents of oral cancer include tobacco and alcohol. This paper reviews the spectrum of molecular changes found in oral squamous cell carcinomas from Western (U.K., U.S.A., Australia) and Eastern (India, S.E. Asia) countries. p53 mutations are common in tumours from the West (47%) but are infrequent in the East (7%). Tumours from India and South East Asia are characterised by the involvement of ras oncogenes, including mutation, loss of heterozygosity (H-ras) and amplification (K- and N-ras), events which are uncommon in the West. The possibility that these genetic differences reflect aetiology and/or ethnic origin is discussed.

Fish oil may be an antidote for the cardiovascular risk of smoking

The fact that the cardiovascular risk of ex-smokers approximates that of non-smokers after two years of abstinence, implies that accelerated atherogenesis is not the chief mechanism of smoking-related heart disease. Indeed, smoking or nicotine have adverse effects on blood rheology, thrombotic risk, coronary blood flow, and risk for arrhythmias. Omega-3-rich fish oils can be expected to correct or compensate for a remarkable number of the adverse impacts of smoking/nicotine: increased plasma fibrinogen, decreased erythrocyte distensibility, increased plasma and blood viscosity, increased platelet aggregability, increased plasminogen activator inhibitor levels, vasoconstriction of the coronary bed, reduced fibrillation threshold, increased triglycerides, reduced high-density lipoprotein cholesterol, and increased production of superoxide by phagocytes. Smokers who cannot overcome their addiction should be encouraged to substitute nicotine aerosols/gum for tobacco and advised to use supplementary fish oil and other cardioprotective nutrients.

Molecular and cellular biomarkers for field cancerization and multistep process in head and neck tumorigenesis

One way to explain the development of head and neck cancer is through the theories of field cancerization, i.e., the exposure of an entire field of tissue to repeated carcinogenic insult, and multistep process, i.e., development of multiple cancers in a predisposed filed through a series of recognizable stages. Recent molecular genetic studies of histologically normal and premalignant epithelia of high-risk subjects and studies of malignant tumors in aerodigestive tract epithelia have identified a continuum of accumulated specific genetic alterations that possibly occur during the clonal evolution of tumors, namely, during the multistep process. Second primary or multiple primary tumors arise in the same fields as independent clones, with similar but unique molecular genetic and/or cellular alterations. Consequently, the assessment of these genetic and phenotypic alterations has been integrated into clinical chemoprevention trials in an effort to identify biomarkers that are also risk predictors and intermediate end points. This review covers candidate biomarkers of the processes of field cancerization and multistep tumor development in aerodigestive tract epithelia, including general and specific genetic markers, proliferation markers, and squamous differentiation markers.

Retinoid actions and implications for prevention and therapy of oral cancer

Squamous cell carcinomas of the oral cavity can be preceded by clinically obvious premalignant changes, and they have a high rate of incidence of development of second primary tumors. Recent studies suggest retinoids not only for the treatment of oral eukoplakia, but also for the prevention of second primaries. Although retinoids are promising therapeutic agents, their therapeutic potential has been limited by their undesirable side-effects. A complete network of nuclear receptors has now been identified that mediate the action of retinoids and can interfere directly with cell proliferation signals by interacting with transcription factors. It has recently been shown that retinoids with receptor-selective activities can be obtained that are likely to have fewer side-effects because of their restricted biologic activities.

Nutrition and lung cancer

Epidemiologic evidence on the relationship between nutrition and lung cancer is reviewed. Observational studies of diet and lung cancer, both prospective and retrospective, continue to suggest strongly that increased vegetable and fruit intake is associated with reduced risk in men and women; in various countries; in smokers, ex-smokers, and never-smokers; and for all histologic types of lung cancer. Prospective studies of blood beta-carotene levels, arguably the best available biomarker of vegetable and fruit intake, indicate that low levels are predictive of increased lung cancer incidence. However, in a randomized, placebo-controlled clinical trial in male smokers, lung cancer incidence and total mortality were increased significantly among the men receiving beta-carotene supplements. If beta-carotene can prevent lung carcinogenesis, which the trial cannot rule out, then the dosage, duration of use, method of administration, and/or subpopulation are critical. Ongoing clinical trials, some of which include women, will provide much-needed information. Other carotenoids, other phytochemicals, and associated dietary patterns may explain the beneficial effects of vegetables and fruits and have not been explored adequately in epidemiologic work. Several observational epidemiologic studies, both prospective and retrospective, have indicated that diets high in fat, saturated fat, and cholesterol may increase the risk of lung cancer and that the effect is not mediated through vegetable and fruit intake. The relationship, although not yet established, merits further investigation. Since beta-carotene can function as an antioxidant, other micronutrients with this potential, specifically vitamins E and C and selenium, also have been proposed to reduce lung cancer risk. However, the totality of the epidemiologic evidence is not, at present, persuasive for any one of these micronutrients.

Use of antioxidant supplements in the treatment of human oral leukoplakia

An increasing public awareness of antioxidants may prompt a patient's request to be treated without surgery if a leukoplakic lesion is discovered. However, surgical excision remains the treatment of choice for oral leukoplakia. The use of antioxidant supplements has shown some promise, but the predictability of success remains uncertain and long-term results are unavailable. Before the decision to use any antioxidant is made, it is critical to obtain a histopathologic diagnosis of the lesion. When dealing with a lesion diagnosed as hyperkeratosis, it may be appropriate to choose an antioxidant that may take some time for clinical improvement to occur. However, as the grade of epithelial dysplasia becomes more severe, consideration must be given to the possibility of malignant transformation during antioxidant treatment. We do not recommend the use of antioxidant supplements in the treatment of any carcinoma. The therapeutic use of antioxidant supplements outside of clinical trials conducted at academic medical centers should be done with considerable caution by practitioners in private practice. It should be emphasized that in these clinical trial patients were seen at frequent intervals to monitor their progress and to intervene if there was a noticeable deterioration in the clinical appearance of the lesion. In spite of the uncertainty with respect to antioxidant treatment, there are circumstances in which it should be considered. Recurrence after surgical excision when there is little reason to believe that a second surgical excision would be any more successful is an ideal candidate. Also, patients with widespread leukoplakia that involves a large area of the oral mucosa might be suitable for treatment with antioxidants, as well as patients who have extensive medical problems that make them surgical risks. The choice of which antioxidant(s) to use is complex because thus far there is no combination that is superior to the others. Beta-carotene with ascorbic acid or alpha-tocopherol is attractive because of a lack of side effects, but the range in reported values for lesion improvement has been broad and the clinical improvement typically takes several months. Clinical response with 13-cRA is faster but requires baseline and periodic serologic testing, as well as close monitoring for side effects. In those circumstances in which time is an important consideration, 13-cRA might be useful because clinical improvement can be evaluated within a matter of weeks as compared with beta-carotene. The group from M.D. Anderson Hospital has shown the value of an induction dose of 13-cRA that is followed by a lower maintenance dose. Unfortunately, the problem of recurrence after discontinuation of 13-cRA is quite common. One aspect that has not been evaluated is the combination of conventional surgical excision and the administration of postoperative antioxidants. This would have the obvious advantage of conventional treatment of surgery together with the possible protective effect of the antioxidants. Although this is an attractive hypothesis, we do not know of any studies that have proven this to be beneficial.

Mutant frequency at the hprt locus in human lymphocytes in a case-control study of lung cancer

A clonal assay to determine the mutant frequency (MF) at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus in human lymphocytes has been used by a number of investigators to study exposure to mutagens and carcinogens in a variety of populations. We have studied hprt MF in 106 subjects (40 controls and 66 cases) enrolled in a case-control investigation of lung cancer. Epidemiological data collected included smoking history, intake of dietary micronutrients, and occupational and environmental exposures as well as medical history, all obtained from an interviewer-administered questionnaire. All subjects were also genotyped for the known polymorphism in glutathione S-transferase class mu (GST-mu). In analysis of cases and controls, hprt MF was not associated with age, smoking, the polymorphism in GST mu, dietary intake, occupational exposures, family history of cancer or usage of medications. Since MF and cloning efficiency (CE) are not independent when CE is low, further analysis in cases and controls with a CE greater than or equal to 30% (27 cases and 22 controls) was also conducted. In analysis of controls, hprt MF increased with age and was inversely associated with intake of folate and vitamins A and C. The presence of lung cancer was not associated with hprt MF. Thus, our study supports the previous observation that dietary components may affect the MF at the hprt locus.

European School of Oncology Advisory report to the European Commission for the Europe Against Cancer Programme: oral carcinogenesis in Europe

A European School of Oncology Advisory Group has reviewed current knowledge on the epidemiology, treatment and prevention of cancer of the oral cavity. While the major factors in the aetiology of such cancers are thought to be well understood, i.e. tobacco and alcohol consumption, current increases in the occurrence of the disease, especially in young adults throughout Europe, are cause for concern. The reasons for such increases are not clearly evident and the Advisory Group has suggested further work which is required to be carried out to understand the aetiology. In treatment of the disease there have been no major improvements in survival for patients in recent decades and the importance of examining new radiotherapy modalities and defining the role of chemotherapy is emphasized. Primary prevention of oral cancer could be achieved by stopping smoking tobacco, limiting alcohol consumption to a minimum (2-3 drinks per day) and increasing intake of fruits and vegetables. To supplement these actions, while neither population screening programmes nor screening trials could be recommended by the Advisory Group, initial chemoprevention trials have produced some promising results and this represents an interesting area which is the focus of much current research.

Evaluation of chemoprevention of oral cancer with Spirulina fusiformis

The blue-green microalgae Spirulina, used in daily diets of natives in Africa and America, have been found to be a rich natural source of proteins, carotenoids, and other micronutrients. Experimental studies in animal models have demonstrated an inhibitory effect of Spirulina algae on oral carcinogenesis. Studies among preschool children in India have demonstrated Spirulina fusiformis (SF) to be an effective source of dietary vitamin A. We evaluated the chemopreventive activity of SF (1 g/day for 12 mos) in reversing oral leukoplakia in pan tobacco chewers in Kerala, India. Complete regression of lesions was observed in 20 of 44 (45%) evaluable subjects supplemented with SF, as opposed to 3 of 43 (7%) in the placebo arm (p < 0.0001). When stratified by type of leukoplakia, the response was more pronounced in homogeneous lesions: complete regression was seen in 16 of 28 (57%) subjects with homogeneous leukoplakia, 2 of 8 with erythroplakia, 2 of 4 with verrucous leukoplakia, and 0 of 4 with ulcerated and nodular lesions. Within one year of discontinuing supplements, 9 of 20 (45%) complete responders with SF developed recurrent lesions. Supplementation with SF did not result in increased serum concentration of retinol or beta-carotene, nor was it associated with toxicity. This is the first human study evaluating the chemopreventive potential of SF. More studies in different settings and different populations are needed for further evaluation.

Oral precancer: preventive and medical approaches to management

Leukoplakias are among the most common potentially malignant oral lesions. Some are idiopathic, others are related to habits such as tobacco and/or alcohol use. Medical management includes reducing or abandoning these habits, increasing the intake of fruit and vegetables in the diet, and possibly the use of active agents. Retinoids, carotenoids and topical cytotoxic agents show promise, and newer therapies are on the horizon.

Micronuclei, a biomarker for chemoprevention trials: results of a randomized study in oral pre-malignancy

Biomarkers are being sought that could serve as surrogate end points for chemoprevention trials. Micronuclei, cytoplasmic fragments of DNA, have been proposed as a biomarker and studied in oral pre-malignancy. This study evaluated micronuclei frequency in a randomized chemoprevention trial of oral pre-malignancy. A recent clinical trial evaluated the responses of pre-malignant oral lesions to 3 months of therapy with isotretinoin followed by 9 months of either low-dose isotretinoin or beta-carotene. For 57 study participants, micronuclei were counted in mucosal scrapings of the lesion and in normal-appearing mucosa at baseline and following 3 months and 12 months of therapy. Micronuclei counts were higher in scrapings from the lesion than in the normal-appearing mucosa. Following 3 months of isotretinoin, the micronuclei counts in scrapings of the lesion were significantly reduced. With treatment, the mean micronuclei count declined at 3 months. In a randomized comparison, both isotretinoin and beta-carotene maintained the suppression of micronuclei. The change in micronuclei count was not associated with the clinical or histological response to treatment. Chemoprevention treatment with isotretinoin led to a reduction in frequency of micronuclei, a marker of recent DNA injury, which was then maintained by both isotretinoin and beta-carotene.

Topical bleomycin treatment of oral leukoplakia: a randomized double-blind clinical trial

BACKGROUND

Oral leukoplakia and oral erythroplakia may be associated with benign and dysplastic cellular changes, and are at risk of malignant transformation. Additional means of management of these lesions is needed. The results of nonblinded trials using topical bleomycin in oral leukoplakia indicated the need for phase III study.

METHODS

A prospective, double-blind, randomized trial of topical bleomycin versus placebo was conducted. Bleomycin 1% in dimethylsulphoxide (DMSO) or the carrier was applied for 5 minutes for 14 consecutive days. Clinical assessment and pre-application and post-treatment biopsies were conducted.

RESULTS

Twenty-two patients were randomized. Of the patients who received bleomycin, decrease in clinical size of the lesion was achieved (p = 0.001), and histological reduction in dysplasia was seen (p = 0.094).

CONCLUSIONS

The topical application of bleomycin in DMSO may represent an additional approach to management of oral leukoplakia. The treatment is well-tolerated, and may be considered when the location or extent of the lesion may make surgical excision difficult.

A clinical trial of antioxidant supplements in the treatment of oral leukoplakia

Seventy-nine patients with oral leukoplakia that was histologically verified as either hyperkeratosis or epithelial dysplasia with hyperkeratosis were enrolled in an antioxidant supplementation program for the treatment of the oral lesions. The patients received 30 mg of beta-carotene, 1000 mg of ascorbic acid, and 800 IU of alpha-tocopherol per day for 9 months. Clinical improvement of the oral lesion was noted in 55.7% of the patients and was more likely to occur in patients who reduced their use of alcohol or tobacco (p = 0.0056). Although risk-factor reduction was important, approximately half of the patients who did not alter their exposure to either alcohol or tobacco showed clinical improvement. The antioxidant supplementation significantly increased serum and tissue levels of beta-carotene, ascorbic acid, and alpha-tocopherol, but these changes did not correlate strongly with clinical improvement.

The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study in Finland

The U.S. National Cancer Institute and the Finnish National Public Institute jointly sponsored a large double-blind, placebo-controlled primary-prevention trial to examine the effects of vitamin E and beta-carotene supplementation on reducing the incidence of lung cancers in male smokers, ages 50-69 years. Supplementation did not result in a significant reduction in lung cancer, and a higher incidence of lung cancer was observed in the group receiving beta-carotene. These results should be examined within the context of the population studied before they are cited as definitive.

Biology and chemoprevention of head and neck cancer

Head and neck cancer remains a common cause of mortality and morbidity in the United States and throughout the world. In spite of advances in the management of patients with advanced disease, overall survival in this group remains poor. Furthermore, although cancer mortality is lower in patients with early-stage disease, treatment results in significant morbidity, and these patients also face the risk of developing a second primary tumor. Chemoprevention is an innovative approach to decrease overall cancer morbidity and mortality using substances that are capable of preventing cancer progression. Head and neck cancer is an excellent model for chemoprevention, as its biology is consistent with the two concepts important for the development of chemoprevention strategies: field cancerization and multistep carcinogenesis. Several classes of compounds have been evaluated in chemoprevention trials. The most frequently studied agents, the retinoids, were found frequently to induce remissions in patients with oral leukoplakia. Furthermore, retinoids prevented progression to malignancy in one randomized maintenance study. Other agents, including beta-carotene and vitamin E, have been found also to have activity in the management of oral leukoplakia. However, the clinical role of chemopreventive agents in reducing cancer mortality remains to be defined. Two studies, one in head and neck cancer and one in lung cancer, have shown the ability of retinoids to prevent the development of second primary tumors. Current large randomized trials are defining the effectiveness of these agents in reducing the mortality of aerodigestive tract tumors in individuals at high risk.