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European Trials on Dietary Supplementationfor Cancer Prevention

GUIDO BIASCOa,c AND GIAN MARIA PAGANELLIb,d

aIstituto di Ematologia ed Oncologia Medica “Ludovico e Ariosto Seràgnoli,” University of Bologna, 40138 Bologna, ItalybDivisione di Pneumologia, Azienda Ospedaliera di Bologna, 40138 Bologna, Italy

ABSTRACT: European institutions aimed at cancer research and control arespending sizable resources to develop preclinical and clinical chemopreventiontrials. Pilot studies showed positive effect on colorectal cell proliferation fromsupplementation with calcium; vitamins A, C, and E; -3 fatty acids; and folicacid. A significant reduction in adenoma recurrence after polypectomy wasfound in patients randomly assigned to take vitamin A, C, and E supplementa-tion or, to a lesser extent, lactulose. Although first reports showed a disquietinghigher incidence of lung cancer in male smokers who took -carotene supple-mentation, the European Organization of Research and Treatment of Cancer(EORTC) planned a chemoprevention study on the prevention of second pri-mary tumors in patients with curatively treated head and neck or lung cancer(EUROSCAN). Retinol palmitate or N-acetylcysteine or both are given for twoyears. The European Cancer Prevention Organization (ECP) is carrying out aclinical trial in patients with previous adenomas of the large bowel, to test theefficacy of calcium or fiber supplementation on adenoma recurrence. ECP incollaboration with EURONUT has also started a multinational interventionstudy of the effect of H. pylori eradication and/or dietary supplementation withvitamin C on intestinal metaplasia.

INTRODUCTION

In recent years, the proposal of using natural or synthetic agents in order to reverseor inhibit cancer development can be considered one of the most important advancesin cancer prevention. Among potential chemopreventive agents, dietary constituentsare often preferred because they are regarded as naturally occurring and safe. In par-ticular, studies on the molecular biology of the neoplastic process focused on the im-portance of micronutrients as candidates for chemoprevention of specific tumors.

Therefore, European institutions conducting cancer research and control spentsizable resources to develop preclinical and clinical chemoprevention trials.1 Be-

cAddress for communication: Istituto di Ematologia ed Oncologia Medica “Ludovico e Ari-osto Seràgnoli,” University of Bologna, Divisione di Pneumologia, Azienda Ospedaliera diBologna, Policlinico S. Orsola-Malpighi, Via Massarenti 9, 40138 Bologna, Italy. Voice: 39-51-6363111 ext. 4078; fax: 39-51-398973.

e-mail: gbiasco@med.unibo.itdDivisione di Pneumologia, Azienda Ospedaliera di Bologna, Policlinico S. Orsola-Malpighi,

Via Palagi 9, 40138 Bologna, Italy. Voice: 39-51-6362465; fax: 39-51-6362557. e-mail: pneumo@orsola-malpighi.med.unibo.it

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cause the definitive end point of cancer chemoprevention is cancer incidence, thesetrials need thousands of patients monitored for several years in order to detect a sig-nificant efficacy of treatment. Pioneer studies were aimed to assay the effect of po-tential chemopreventive substances on intermediate end points that are associatedwith cancer risk, among which are cell proliferation abnormalities.

CELL PROLIFERATION AS AN INTERMEDIATE BIOMARKER IN CHEMOPREVENTION STUDIES OF COLORECTAL CANCER

The first report of a normalization of rectal cell proliferation as an intermediatechemopreventive effect was done by Martin Lipkin and Harold Newmark in 1985,using a 1.5–2 g/day dietary calcium supplementation. These results were confirmedby other trials, some of which were carried out in Europe.2

In 1992, a pilot study carried out at the University of Bologna suggested that an-tioxidant vitamins are able to reduce the expansion of the proliferative compartmentof the rectal mucosa, which is frequently found in conditions at increased risk of col-orectal cancer. In this trial, vitamins A, C, and E were given daily for 6 months atdoses of 30,000 IU, 1000 mg, and 70 mg, respectively, to patients with previous ad-enomas of the large bowel after colonoscopic polypectomy.3

Similarly, another preclinical study was carried out in Italy on the basis of the ep-idemiological evidence of an inverse correlation between the consumption of seafoodand colorectal cancer incidence. In this study, the supplementation of fish oil rich inΩ-3 fatty acids reduced the expansion of the proliferative compartment of the rectalmucosa of subjects at increased risk of colorectal cancer.4 We also mention a studythat showed that short-chain fatty acids, such as butyric acid, are able to reduce in-flammation and mucosal hyperproliferation in patients affected by ulcerative colitis.5

It has been suggested that increased colon cancer risk in ulcerative colitis is cor-related to a reduced bioavailability of folate, presumably because of an impaired ab-sorption induced by a common medication, sulfapyridine. Recently, we studied theeffect of folate supplementation on rectal cell proliferation of patients with long-standing ulcerative colitis, which are at increased risk of colorectal cancer. In thispilot trial, the administration of folic acid (as calcium folate 15 mg/day for 3 months)was able to normalize cell kinetic abnormalities, whereas no significant change wasobserved in the placebo group.6

These preliminary results gave impulse to the development of phase II clinical tri-als aimed at evaluating the effect of dietary consituents and/or micronutrients on lat-er end points related to cancer development, that is, epithelial dysplasia, or therecurrence of cancer or second primary malignancies of the gastrointestinal tract andrespiratory system.

BETA-CAROTENE AND LUNG CANCER: WHAT’S GOING WRONG?

Epidemiological evidence indicates that the consumption of diets rich in caro-tenoids; selenium; and vitamins A, C, and E are associated with reduced lung cancerrisk. On the basis of these findings, large chemoprevention trials were planned in the

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1980s and early1990s. In 1994 the results of a Finnish study (sponsored by the Na-tional Public Health Institute of Finland with the United States National Cancer Insti-tute) were published on the effect of α-tocopherol and β-carotene on male smokers.The report was quite disquieting: a minimal reduction in lung cancer incidence wasdemonstrated in men who received vitamin E, but, by contrast, an 18% higher inci-dence of lung cancer and an 8% higher total mortality were found among the subjectswho took 20 mg/daily of β-carotene. Subjects who took both vitamin E and β-caro-tene showed an increase in lung cancer similar to those with β-carotene alone, sug-gesting the absence of any significant interaction between those supplements.7

These results were further confirmed by the United States CARET trial, whichwas therefore abruptly stopped.8 However, additional analyses of these studiespointed out that we cannot exclude the possibility that the increase of lung cancerincidence observed in the β-carotene supplementation arms was due to active smok-ing throughout the period of intervention in a large proportion of subjects. As a mat-ter of fact, the percentage of current smokers at the beginning and at the end of thestudy were 100–80% in the ATBC study and 80–48% in the CARET study. Becauseit is possible to hypothesize an increase of metabolic activation of carcinogens fromtobacco smoke by high-dose β-carotene or a promoter effect at a later carcinogeneticstep, some authors suggested that it is mandatory to concentrate future chemopreven-tion programs on former smokers before endorsing a causative role by β-carotene.9

CHEMOPREVENTION OF HEAD, NECK, AND LUNG CANCERS

In 1988 the European Organization of Research and Treatment of Cancer (EORTC)began a chemoprevention study on the prevention of second primary tumors in patientswith head and neck or lung cancer (EUROSCAN). This was a double-blind controlledstudy with a 2 × 2 factorial design, started in June 1988, which recruited patients cur-atively treated with oral, laryngeal, or lung cancer. Retinol palmitate, 300,000 IU/daily,was given for one year and 150,000 IU/daily for another year, or N-acetylcysteine(NAC), 600 mg/daily, for two years, or both drugs. The end points of this study are therate of recurrence and occurrence of second primary tumors. More than 60 centersfrom 14 European countries participated in the study. At present, no data are availablein the literature, although the end of the intervention period was expected to be aroundthe end of 1996.10 However, the investigators are optimists, on the basis of experimen-tal and clinical data regarding the two agents. As a matter of fact, high-dose retinolpalmitate was used in an adjuvant trial of surgically resected stage I lung cancer. Aftera median follow-up of 46 months, a reduction in the percentage of recurrence, or oc-currence of new primary tumors, was found in patients treated with retinol palmitate,300,000 IU/day, for one year, as compared to the control group.11

CHEMOPREVENTION OF METACHRONOUS ADENOMASOF THE LARGE BOWEL

Concerning the effect of antioxidant vitamins in large-bowel carcinogenesis,Roncucci et al. showed a significant reduction in adenoma recurrence in 209 patients

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who were followed for at least 12–18 months after polypectomy. Patients were ran-domly chosen to take either vitamins A (30,000 IU daily), C (1000 mg/daily), and E(70 mg) or lactulose (20 mg/daily). A decrease in adenoma recurrence rate wasfound in both arms but was remarkably higher in vitamin-treated patients; however,a low compliance rate was observed.12

A European multicentric intervention study on chemoprevention of colorectalcancer is currently in progress, conducted by the European Cancer Prevention Orga-nization (ECP). This is a double-blind, placebo-controlled clinical trial with a paral-lel design, which recruited patients aged 35–75 with adenomas of the large bowelpreviously removed by colonoscopy and a clean colon at entry. The main aim of thestudy is to test the efficacy of oral calcium supplementation (2 g/day as calcium glu-conolactate and carbonate) or oral dietary supplementation with fiber (as 3.8 g/dayisphagula husk) on adenoma recurrence. Secondary end points are the effect of treat-ment on rectal cell proliferation and on concentration of bile acids and sterols instools. All randomized patients are followed up every 6 months for 3 years. At thebeginning and at the end of the study, a colonoscopy is performed and rectal biopsiesare taken for cell proliferation analysis (PCNA immunostaining and, when possible,bromodeoxyuridine uptake). Blood samples are obtained for biochemical analyses,including DNA analysis; stool samples are collected for quantitative analysis of bileacids and related compounds; and a dietary questionnaire is administered. Addition-al blood samples are drawn annually to assess the tolerability of the treatments (e.g.,calcaemia, and liver and kidney function). Up to now, about 700 subjects have beenincluded from Belgium, Denmark, France, Germany, Ireland, Israel, Italy, Portugal,Spain and the United Kingdom; there were only nine cases of important side effects,which consisted of major diarrhea or severe abdominal pain that disappeared afterdiscontinuation of intervention.13

PERSPECTIVES OF CHEMOPREVENTION OF GASTRIC CANCER:THE ECP-IM STUDY

In 1985 the European Cancer Prevention Organization (ECP) in collaborationwith EURONUT set up a case-control study to study the relationship between dietand intestinal metaplasia as a precursor of epithelial dysplasia and gastric cancer. Forevery intestinal metaplasia case there were two controls matched for age, gender, andresidence. Endoscopy and biopsies were performed as well as diet and lifestyle as-sessment; serum, urine, and gastric juice samples were also collected. From the firstphase of the study, it was concluded that when compared to controls, cases with in-testinal metaplasia had a low intake of fresh fruit and vegetables, a very low intakeof vitamin C, and a high prevalence of H. pylori antibodies.14 In light of these re-sults, ECP has started a large multinational intervention study of the effect of H. py-lori eradication and/or dietary supplementation with vitamin C on the gastricmucosal histopathology in patients with intestinal metaplasia.15 Patients will be ran-domly assigned as follows: H. pylori–negative patients will be administered 1 g vi-tamin C daily for 3 years vs placebo; H. pylori–positive patients will be given a 2-week eradication regimen (omeprazole, 20 mg twice daily, and clarithromycin,500 mg, three times daily), then either vitamin C or placebo. The hypotheses to be

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tested are that H. pylori eradication causes a statistically significant change in thepattern of intestinal metaplasia, ascorbic acid supplementation causes a statisticallysignificant change in the pattern of intestinal metaplasia, and there is an interactionbetween the two regimens (H. pylori eradication and vitamin C supplementation).

In conclusion, the large clinical chemoprevention trials are actually being com-pleted in Europe, and in the next few years we are expecting to obtain more infor-mation on the efficacy of chemoprevention with dietary constituents and on thefeasibility of such programs on large population groups at increased risk of cancerdevelopment.

REFERENCES

1. BUIATTI, E., D. BALZI & A. BARCHIELLI. 1994. Intervention trials of cancer preven-tion: Results and new research programmes. IARC Technical Report 18, Lyon.

2. O’SULLIVAN, K.R., P.M. MATHIAS, S. BEATTIE & C. O’MORAIN. 1993. Effect of oralcalcium supplementation on colonic crypt cell proliferation in patients with adenom-atous polyps of the large bowel. Eur. J. Gastroenterol. Hepatol. 5: 85–89.

3. PAGANELLI, G.M. G. BIASCO, G. BRANDI et al. 1992. Effect of vitamin A, C, and Esupplementation on rectal cell proliferation in patients with colorectal adenomas. J.Natl. Cancer Inst. 84: 47–51.

4. ANTI, M., G. MARRA, F. ARMELAO et al. 1992. Effect of Ω-3 fatty acids on rectalmucosal cell proliferation in subjects at risk for colon cancer. Gastroenterology 103:883–891.

5. SCHEPPACH, W., H. SOMMER, T. KIRCHNER et al. 1992. Effect of butyrate enemas onthe colonic mucosa in distal ulcerative colitis. Gastroenterology 103: 51–56.

6. BIASCO, G., U. ZANNONI, G.M. PAGANELLI et al. 1997. Folic acid supplementation andcell kinetics of rectal mucosa in patients with ulcerative colitis. Cancer Epidemiol.Biomarkers Prev. 6: 469–471.

7. THE ALPHA-TOCOPHEROL, BETA-CAROTENE CANCER PREVENTION STUDY GROUP. 1994.The effect of vitamin E and beta carotene on the incidence of lung cancer and othercancers in male smokers. N. Engl. J. Med. 330: 1029–1035.

8. OMENN, G.S., G.E. GOODMAN, M.D. THORNQUIST et al. 1996. Effects of a combinationof beta carotene and vitamin A on lung cancer and cardiovascular disease. N. Engl. J.Med. 334: 1150–1155.

9. PASTORINO, U. 1997. β-carotene and the risk of lung cancer. J. Natl. Cancer Inst. 89:456–458.

10. DE VRIES, N., U. PASTORINO & N. VAN ZANDWIJK. 1994. Chemoprevention of secondprimary tumors in head and neck cancer in Europe: EUROSCAN. Eur. J. Cancer B(Oral Oncol.) 6: 367–368.

11. PASTORINO, U., M. INFANTE, M. MAIOLI et al. 1993. Adjuvant treatment of stage Ilung cancer with high-dose vitamin A. J. Clin. Oncol. 11: 1216–1222.

12. RONCUCCI, L., P.D. DI DONATO, L. CARATI et al. 1993. Antioxidant vitamins orlactulose for the prevention of the recurrence of colorectal adenomas. Dis. ColonRectum 36: 227–234.

13. FAIVRE, J., C. COUILLAULT, O. KRONBORG et al. 1997. Chemoprevention of metach-ronous adenomas of the large bowel: Design and interim results of a randomizedtrial of calcium and fibre. Eur. J. Cancer Prev. 6: 132–138.

14. HILL, M.J. ON BEHALF OF THE ECP-EURONUT-IM STUDY GROUP. 1997. ECP-EURONUT study of diet and intestinal metaplasia. Eur. J. Cancer Prev. 6: 201–204.

15. REED, P.I. 1994. The ECP-IM Intervention Study. Eur. J. Cancer Prev. 3 (Suppl.2):99–104.