Chemoprevention in the management of oral cancer: EUROSCAN and other studies

Enhanced levels of glutathione and protein glutathiolation in rat tongue epithelium during 4-NQO-induced carcinogenesis

High glutathione (GSH) levels are commonly found in oral tumors and are thought to play an important role in tumorigenesis. While posttranslational binding of GSH to cellular proteins (protein glutathiolation) has recently been recognized as an important redox-sensitive regulatory mechanism, no data currently exist on this process during carcinogenesis. Our goal was to determine the effects of 4-nitroquinoline-N-oxide (4-NQO)-induced carcinogenesis on tongue levels of protein-bound and free GSH and related thiols in the rat. Male F-344 rats (6 weeks of age) were administered either 4-NQO (20 ppm) in drinking water or tap water alone (controls) for 8 weeks. Twenty-four weeks after cessation of 4-NQO, squamous cell carcinomas of the tongue were observed in all rats. The levels of both free and bound GSH in tumors, as well as in adjacent tissues, were 2- to 3-fold greater than in tongue epithelium from control rats (p < 0.05). Prior to tumor formation, at 8 weeks after cessation of 4-NQO, hyperplasia, dysplasia and carcinoma in situ were observed in 100%, 25% and 12.5% of 4-NQO-treated rats, respectively. At this early stage of carcinogenesis, levels of free and bound GSH were increased 50% compared with tongue tissues from control rats (p<0.05). Glutathione disulfide (GSSG) levels were also 2-fold greater in tongue tissues from 4-NQO treated vs. control rats (p<0.05). Altogether, these results suggest that protein glutathiolation, together with GSH and GSSG levels, are induced during oral carcinogenesis in the rat possibly as a result of enhanced levels of oxidative stress.

Overview of past, present and future of the EORTC Lung Cancer Group. European Organisation for Research and Treatment of Cancer

The EORTC Lung Cancer Group (LCG) is a multidisciplinary international group of experts performing clinical research in lung cancer since 1962. Originally, the group consisted mainly out of French and Belgian investigators and expanded gradually into a wide range of investigators from all European Union countries, as well as some investigators from Switzerland, Poland, Czech Republic, Egypt, Slovenia, South Africa, Peru, Brazil and Cyprus. Despite the wide collaboration, it remains a difficult task to perform high quality large clinical research trials to answer important scientific questions in the treatment of lung cancer. For this reason, the EORTC Lung Cancer Group has invested a lot of efforts in promoting worldwide, randomised phase III studies in collaboration with other Groups. Furthermore, the LCG promotes small phase II trials of new drugs or treatments for lung cancer and stimulates the investigation of new strategies and treatments for rare intrathoracic malignancies.

The epidemiology of lip cancer: a review of global incidence and aetiology

Lip cancer (140 ICD-9) is a form of oral cancer that has a distinctive global epidemiology. This review summarises global incidence rates for male and female lip cancer with the aid of cancer atlases. High male lip cancer rates are reported for regions of North America (12.7 per 100 000 per annum), Europe (12.0 per 100 000 per annum) and Oceania (13.5 per 100 000 per annum), while it is virtually unknown in parts of Asia. Factors commonly cited as important in the aetiology of lip cancer include solar radiation, tobacco smoking and viruses. An attempt is made to summarise the evidence for factors that may be important in lip carcinogenesis. While incidence rates are generally stable or falling among males worldwide, they are rising in many female populations. The aetiology of the disease is far from established and much information regarding its pathogenesis is based on anecdotal rather than case-controlled epidemiological evidence. The epidemiology of lip cancer supports the proposal that the lip should be considered as a distinct cancer site, rather than being included with other forms of intraoral cancer.

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.

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.

Early diagnosis and prevention of oral cancer and precancer: report of Symposium III

Oral precancer encompasses several conditions and lesions. Among those entities included in the concept are leukoplakia, erythroplakia, lichen planus, and submucous fibrosis. For prevention, knowledge about etiologic and pathogenetic factors is imperative. It is well-known that excessive consumption of tobacco and alcohol has a bearing on the development of oral leukoplakia and probably also of erythroplakia. However, among leukoplakias, the idiopathic or cryptogenic type probably shows the most serious malignant potential. Involved in the development of such lesions may be general nutritional aspects, e.g., proper utilization of vitamin A. It is also well-known that iron deficiency has been linked to Plummer-Vinson's syndrome, showing a precancerous trait. Among factors involved in the pathogenesis of lichen planus is probably mental stress. Thus, stress factors and related neurological components have been linked to the immunological system. Lifestyle factors, such as nutrition, tobacco, and alcohol, and also mental environment may be of importance for the development of oral precancer and cancer.

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.

Risk of multiple primary tumors following oral squamous-cell carcinoma

The follow-up of 727 patients with squamous-cell carcinoma (SCC) of the lip and oral cavity has been used for the risk analysis of multiple primary tumors (MPTs) following SCC of the lip and oral cavity. Age-, gender- and site-specific cancer-incidence rates from the general population have been applied to the appropriate persons-years of follow-up of patients with SCC of the lip and oral cavity. The study indicates that patients with a primary SCC of the lip and oral cavity have, compared with the general population, a significantly elevated risk of developing an additional cancer of the oral cavity and/or pharynx, the risk being 74.7-fold for males and 190.4-fold for females. Furthermore, a 24.6 and 45.3 times higher risk of an additional esophageal tumor was found in males and females respectively. The risk of cancer of the lung and pharynx was less elevated compared with the risk of cancer of the upper digestive tract. No elevated risks were established in organs outside the respiratory and upper digestive tract.

Prevention of second primary tumours with etretinate in squamous cell carcinoma of the oral cavity and oropharynx. Results of a multicentric double-blind randomised study

Patients who are cured from head and neck carcinomas remain at high risk for developing a second primary in the head and neck area. It is now clear that retinoids exert a prophylactic action on the development of epithelial cancers when tested on laboratory animals and on human premalignant lesions. They are now used in the chemoprevention of epithelial cancers in randomised trials evaluating their efficacy. We prospectively studied 316 patients who developed squamous cell carcinoma of the head and neck, classified as T1/T2, N0/N1 < or 3 cm, M0 according to the UICC TNM classification. Patients were randomly assigned to receive orally, either etretinate (a loading dose of 50 mg/day for the first month, followed by a dose of 25 mg/day in the following months) or a placebo for 24 months. Adjuvant treatment began no later than 15 days after surgery and/or the initiation of radiotherapy. The 5-year survival rate and disease-free survival rate are similar in the two groups. There are no significant differences regarding either local, regional and distant relapses. After a median follow-up of 41 months (range 0-81), 28 patients in the etretinate group and 29 in the placebo group developed a second cancer with, respectively, 12 and 13 in the head and neck region. Adjuvant treatment was definitively discontinued mainly due to toxicity in 33% of patients in the etretinate group versus 23% in the placebo group (P < 0.05). Etretinate, a second-generation retinoid, does not prevent second primary tumours in patients who have been treated for squamous cell carcinoma of the oral cavity and oropharynx.

Development of chemopreventive agents for lung and upper aerodigestive tract cancers

The lung and upper aerodigestive tract (oral cavity, larynx, pharynx, upper esophagus) will harbor the greatest proportion (approximately 20%) of estimated new cancer cases in 1992. The estimated mortality rate is even higher (32%), which is reflected in a 5-year survival rate of only 7% and 12% for esophageal and lung cancer, respectively. Tobacco use appears to remain the major cause of aerodigestive cancers despite efforts at primary prevention--cessation of exposure. Another strategy to decrease this public health problem is secondary prevention or chemoprevention. Cancer chemoprevention is defined as intervention with chemical agents before invasion to halt or slow the carcinogenic process; potential agents may include minor dietary constituents and pharmaceuticals. The main objective of the Division of Cancer Prevention and Control (DCPC), National Cancer Institute, is to develop promising chemopreventive drugs for use in humans. The testing of cancer chemopreventives for efficacy in the clinic differs from that of cancer treatment drugs. Chemopreventive drug trials involve healthy target populations, and the endpoints are reduced cancer incidence or mortality, or increased latency, with no to minimal toxicity. The lung and upper aerodigestive tract represent a unique opportunity for intervention in this setting. Even with cessation of tobacco exposure, the risk of cancer in the entire epithelium remains high for years due to the "field cancerization" effect. Some of the first chemopreventive trials made use of this system due to the availability of a study population with a tissue at demonstrably high risk for malignant progression. Much of the evidence for chemopreventive efficacy is in the oral cavity because of the well-defined epithelial neoplastic progression, the existence of well-established preclinical models, and relative ease of tissue monitoring and sampling. In one of the first randomized trials, Hong and co-workers demonstrated that 13-cis-retinoic acid prevents the appearance of second primary tumors in patients previously treated for squamous cell carcinomas of the oral cavity and upper respiratory tract. Even using a high risk population, chemoprevention trials involve large sample sizes, lengthy duration and follow-up, and high cost. To circumvent these problems, the use of intermediate biomarkers as surrogate endpoints is being explored. Intermediate biomarkers are defined as biological alterations in tissue (histological, genetic, biochemical, proliferative, differentiation-related) occurring prior to cancer development. In the oral cavity, studies using modulation of a histological intermediate biomarker, dysplastic leukoplakia, as the endpoint have demonstrated response to a retinoid.(ABSTRACT TRUNCATED AT 400 WORDS)