Affiliations of authors: W. You, M. H. Gail, J. F. Fraumeni, Jr., Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda MD; L. Zhang, Y. Chang, J. Ma, J. Li, M. Jin, G. Xu, Beijing Institute for Cancer Research and School of Oncology, Beijing Medical University, China; W. Liu, Linqu Public Health Bureau, Shandong, China; Y. Hu, Westat, Rockville, MD; C. Yang, Rutgers University, Piscataway NJ; M. J. Blaser, Vanderbilt University School of Medicine and Department of Veterans Affairs Medical Center, Nashville, TN; P. Correa, Louisiana State University Medical Center, New Orleans; W. J. Blot, International Epidemiology Institute, Rockville.
Correspondence to: Wei-cheng You, M.D., National Institutes of Health, EPS, Rm. 8030, Bethesda, MD 20892-7244 (e-mail: youw{at}mail.nih.gov).
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Herein we report the results of a 4.5-year follow-up study designed to identify factors that influence the progression of gastric precursor lesions to dysplasia and gastric cancer in this high-risk population.
![]() |
SUBJECTS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
During the period from November 1989 through March 1990, a total of 3433 subjects participated in a gastric cancer-screening study, representing 83% of eligible residents aged 3564 years in 14 villages selected at random within four townships of Linqu County, as described previously (3). The study was approved by the Institutional Review Board of both the National Cancer Institute and the Beijing Institute for Cancer Research (BICR), and all subjects gave written informed consent. In brief, after the names of all of the residents were transcribed from village population rosters, health workers visited each person, explained the study, and invited participation in a gastric cancer-screening program; willing individuals received physical and endoscopic examinations. Three experienced gastroenterologists using a fiberoptic gastroscope (Olympus) in 19891990 and 1994 performed the endoscopic examinations. The gastric mucosa was observed, and seven biopsy specimens were obtained from standard locations of the stomach: two in the body of the stomach, one in the angulus, and four in the antrum. After the endoscopic examination in 19891990, participants were followed with systematic monitoring of death and cancer occurrences. In the autumn of 1994, a repeat endoscopic examination employing the same endoscopic procedures as those used in 19891990 was offered to all cohort members (7).1
Pathology
Histopathologic diagnoses of gastric lesions were made in 1994 by the same three pathologists who conducted the 1989 survey at the BICR, and quality-control slides were reviewed by reference pathologists from China and the United States (7). The presence or absence of superficial gastritis, chronic atrophic gastritis, intestinal metaplasia, dysplasia, or gastric cancer was recorded for each biopsy specimen, and each subject was assigned a global diagnosis based on the most severe diagnosis among any of the biopsy specimens. Details of the pathologic procedures and classification criteria, along with photographs of superficial gastritis, chronic atrophic gastritis, intestinal metaplasia, dysplasia, and gastric cancer, and quality-control procedures are provided elsewhere (3,7). Since none of the subjects had a completely normal gastric mucosa and only 1.6% of the subjects had superficial gastritis as the most severe diagnosis, we combined superficial gastritis and chronic atrophic gastritis into one category. The cohort was divided into three groups based on the 1989 pathology: 1) superficial gastritis or chronic atrophic gastritis (n = 1240), 2) intestinal metaplasia (n = 842), and 3) dysplasia (n = 546).
Serum Samples
During the physical examination at baseline, approximately 15 mL of blood was collected from each fasting subject. The blood specimen was allowed to clot for 3040 minutes at room temperature in a dark place and then centrifuged at 965g for 15 minutes. The resulting serum was separated into nine vials, stored immediately at -20 °C, and then moved into a -70 °C freezer within 2 or 3 days. A meta-phosphoric acid solution (6%) was immediately added to the appropriate vial for the vitamin C assay. In approximately 450 randomly selected subjects of 3433 screened subjects, 13% of the total screened population, we measured serum micronutrients.
Laboratory Analysis
Micronutrients. The analysis of fat-soluble vitamins was carried out at BICR, and quality-control assays were done at Rutgers University, Piscataway, NJ, in 19911992 on a 10% sample (5). A high-performance liquid chromatography (HPLC) method developed by Yang and Lee (8) was used on duplicate 150-µL serum samples. Ascorbic acid concentrations were determined at Rutgers University according to the HPLC method of Zhang et al. (9). Trace elements were assayed at the Beijing Metal Institute, China, by neutron activation, and quality control was carried out at the National Toxicologic Laboratory, Quebec, Canada. Ferritin was assayed (10) at the Nutrition Department of the Beijing Medical University, and quality-control samples were assayed at the University of Washington, Seattle.
H. pylori antibody assay. Details of the serologic assay are described elsewhere (5). Briefly, H. pylori strains cultured from gastric biopsy specimens from two patients in Linqu County were used to provide a local antigen preparation for serology. Serum H. pylori immunoglobulin G (IgG) and immunoglobulin A (IgA) antibody concentrations were each measured twice at baseline at BICR in 19911992 with the use of enzyme-linked immunosorbent assay (ELISA) procedures. Quality-control samples were assayed at Vanderbilt University, Nashville, TN. Each assay value was based on the mean of duplicate readings, and the mean of the two assay values was used to assess positivity. An individual was considered to be positive if the mean ELISA optical density reading for either the IgG or IgA was above 1.0, a cutoff based on examination of the distribution of such readings in relation to a group of H. pylori-negative persons and reference sera.
Statistical Analysis
Means and/or geometric means and standard deviations for each serum element were calculated for groups defined by 19891990 baseline and 1994 global histologic diagnoses. Micronutrient levels and logarithms of serum levels of ascorbic acid, ß-carotene, and ferritin were compared with the use of the Student's t tests. Associations of the serum tertiles of the various nutrients, the presence of H. pylori, and other variables related to the risk of progression from baseline superficial gastritis, chronic atrophic gastritis, or intestinal metaplasia to dysplasia or gastric cancer were estimated by odds ratios (ORs). Adjusted OR and 95% confidence interval (CI) estimates were obtained by logistic regression analysis in an SAS program (SAS Institute, Inc., Cary, NC) (11). The ORs were adjusted for subjects' sex, age (3444, 4554, or 55 years), number of cigarettes smoked per day (0, 119, or
20), and 1989 baseline gastric status (0 = superficial or chronic atrophic gastritis or 1 = intestinal metaplasia). There was no adjustment for the number of cigarettes smoked per day in the analysis of smoking duration, however. Age was included as a categorical variable, whereas smoking and exposures classified in tertiles were coded as 0, 1, or 2 for trend tests with 1 df. All P values were two-sided and were considered to be statistically significant at the .05 level.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Most information on baseline cigarette smoking and other variables was available for 2436 subjects, although occasional subjects with missing covariates (27 subjects missing in income and three in cigarette smoking or alcohol consumption categories) were excluded from analyses requiring covariate adjustment. Baseline and follow-up H. pylori antibody status was available for 1889 subjects. Because less than 15-mL blood samples were collected from a number of subjects, baseline data for specific micronutrients were available for 366 subjects for ascorbic acid, 387 subjects for copper, and from 430 to 434 subjects for other micronutrients, respectively.
Smoking duration (OR = 1.6 for 25 years [95% CI = 1.02.1]; trend test, P = .04) and the presence of H. pylori at baseline (OR = 1.8 [95% CI = 1.22.6]) were associated with progression to dysplasia or gastric cancer during the 4.5-year follow-up (Table 1
). The OR for progression to dysplasia or gastric cancer was elevated among subjects who smoked 20 or more cigarettes per day, but it was not statistically significant (OR = 1.4 [95% CI = 0.92.3]; trend test, P = .12). Similar trends were obtained for duration of smoking and number of cigarettes smoked per day with adjustment for H. pylori in addition to age, sex, alcohol consumption, and baseline histopathology. There was no clear evidence that subjects' income, education, or alcohol consumption at baseline was related to the risk of progression to dysplasia or gastric cancer.
|
|
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
This study was designed to evaluate the association of baseline H. pylori status with risk of progression of precancerous gastric lesions. H. pylori prevalence was measured only in 1989 and 1994. A study with multiple H. pylori measurements between 1989 and 1994 could evaluate repeated H. pylori values as risk predictors. In our study, the H. pylori prevalence fell from 71.9% in 19891990 to 67.1% in 1994. Thus, some individuals who had positive serology at baseline became seronegative. These serum conversions do not change substantially the nearly twofold increases in risk associated with baseline seropositivity, however.
Our follow-up study also indicated that cigarette smoking is a risk factor for progression to dysplasia or gastric cancer, whereas there was no clear evidence implicating alcohol consumption. Although not all epidemiologic studies of gastric cancer have found an association with cigarette smoking, a preponderance of evidence indicates that the risk of gastric cancer is moderately increased among smokers (2123). In our casecontrol study of gastric cancer in Linqu (2), smoking at least one pack of cigarettes per day increased the risk of gastric cancer by 50%.
In addition, our cohort study revealed an inverse association between serum vitamin C levels and the subsequent risk of progression to dysplasia or gastric cancer. This finding is consistent with the results of our earlier studies of gastric cancer and precursor lesions in Linqu (2,5) as well as studies in other countries (24). In casecontrol studies in the U.K., plasma ascorbic acid concentrations were statistically significantly lower in patients with intestinal metaplasia than in control subjects (25), whereas gastric juice concentrations of vitamin C were markedly lower in subjects with chronic atrophic gastritis than in subjects with normal gastric mucosa, especially when intestinal metaplasia also was present (26). In Colombia, however, serum vitamin C levels differed only minimally between subjects with chronic atrophic gastritis/intestinal metaplasia or dysplasia and those with normal or superficial gastritis mucosa (27). To our knowledge, the only prospective study that has been reported on the relation of dietary vitamin C intake to gastric cancer (n = 26) (24) suggested a protective effect of vitamin C intake after more than 7 years of follow-up. Although deficiencies in vitamin C were observed in the population from Linqu (5), the highest tertile level in our study was close to that reported for the U.S. population (28) based on measurements of serum micronutrients. This finding suggests that vitamin C, or the specific foods that provide this micronutrient, may reduce the risk of dysplasia and gastric cancer.
We were unable to confirm the suggestion from our earlier baseline study (6) that high levels (the top tertile) of serum ß-carotene are negatively associated with the prevalence of intestinal metaplasia or dysplasia (6). Although four cohort studies showed an inverse association between serum ß-carotene levels and the subsequent risk of gastric cancer, no protective effect was found in two intervention trials [reviewed in (24)]. It is possible that other components of ß-carotene-containing food, such as vitamin C, may protect against gastric cancer and its precursors because estimated vitamin C and ß-carotene contents in food are highly correlated (r = .6; P<.01) (2). There was a suggestion of increased risk of progression of precancerous gastric lesions with elevated vitamin E levels, although the association was not statistically significant. Although vitamin E has been shown to inhibit forestomach carcinogenesis in rats, most epidemiologic studies of gastric cancer, including an intervention trial, have not shown a protective effect of vitamin E (24,25).
Our earlier baseline study (6) noted an inverse association between serum concentrations of ferritin and the prevalence of intestinal metaplasia or dysplasia. Although our cohort study indicated a trend in the same direction, the risks were not statistically significant. In reports from Japan (29) and Hawaii (30), the risk of gastric cancer also was inversely related to prediagnostic serum ferritin levels, but the possible effects of blood loss from gastric lesions, other confounding variables, and limited sample size need to be considered.
A strength of our follow-up study is that the sampling of 14 villages at random from Linqu County ensured a representative population, while the cohort design permitted the study of factors that influence transition rates. Although the availability of baseline histopathology, H. pylori status, and serum micronutrient concentrations provided important advantages over previous studies, the fact that fewer than 500 subjects had micronutrient assays limited the power to evaluate specific relationships with dysplasia and gastric cancer and statistical interactions between variables, such as vitamin C and the presence of H. pylori (31).
In conclusion, our gastroscopy-based cohort study in Linqu County, an area with a high incidence of gastric cancer, revealed that H. pylori infection and cigarette smoking are risk factors for the progression of precursor lesions to dysplasia and gastric cancer, whereas high levels of serum ascorbic acid are protective. In our ongoing randomized, multi-intervention trial in Linqu (32), it will be possible to evaluate whether the eradication of H. pylori and/or the use of a supplement that contains vitamins C and E plus selenium will inhibit the progression of precancerous gastric lesions.
![]() |
NOTES |
---|
Supported in part by Public Health Service (PHS) contracts N01CP15620, N01CP05631, N01CP95660, N01CP21009, and N01CP33041 (National Cancer Institute) and by PHS contract R01DK53707 (National Institute of Diabetes and Digestive and Kidney Diseases), National Institutes of Health, Department of Health and Human Services.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1 Li LD, Lu FZ, Zhang SW, Mu R, Sun ST, Houng-Pu XM, et al. Cancer mortality trends in China, 19731992. Chinese J Oncol 1997;19:39.
2 You WC, Blot WJ, Chang YS, Ershow AG, Yang ZT, An Q, et al. Diet and high risk of stomach cancer in Shandong, China. Cancer Res 1988;48:351823.[Abstract]
3 You WC, Blot WJ, Li JY, Chang YS, Jin ML, Kneller R, et al. Precancerous gastric lesions in a population at high risk of stomach cancer. Cancer Res 1993;53:131721.[Abstract]
4 Kneller RW, You WC, Chang YS, Liu WD, Zhang L, Zhao L, et al. Cigarette smoking and other risk factors for progression of precancerous stomach lesions. J Natl Cancer Inst 1992;84:12616.[Abstract]
5 Zhang L, Blot WJ, You WC, Chang YS, Liu XQ, Kneller RW, et al. Serum micronutrients in relation to pre-cancerous gastric lesions. Int J Cancer 1994;56:6504.[Medline]
6 Zhang L, Blot WJ, You WC, Chang YS, Kneller RW, Jin ML, et al. Helicobacter pylori antibodies in relation to precancerous gastric lesions in a high-risk Chinese population. Cancer Epidemiol Biomarkers Prev 1996;5:62730.[Abstract]
7 You WC, Li JY, Blot WJ, Chang YS, Jin ML, Gail ML, et al. Evolution of precancerous lesions in a rural Chinese population at high risk of gastric cancer. Int J Cancer 1999;83:6159.[Medline]
8 Yang CS, Lee MJ. Methodology of plasma retinol, tocopherol, and carotenoid assays in cancer prevention studies. J Nutr Growth Cancer 1987;4:1927.
9 Zhang L, Lee ML, Yang CS, You WC. A new method to determine ascorbic acid in human serum by HPLC. Chinese Med J Prev Med 1990;25:1834.
10 Addision GM, Beamish MR, Hales CN, Hodgkins M, Jacobs A, Llewellin P. An immunoradiometric assay for ferritin in the serum of normal subjects and patients with iron deficiency and iron overload. J Clin Pathol 1972;25:3269.[Medline]
11 Breslow NE, Day NE. Statistical methods in cancer research: the analysis of casecontrol studies. IARC Sci Publ 1980;32:1338.
12 Nomura A, Stemmermann GN, Chyou PH, Kato I, Perez-Perez GI, Blaser MJ. Helicobacter pylori infection and gastric carcinoma among Japanese Americans in Hawaii. N Engl J Med 1991;325:11326.[Abstract]
13 Siman JH, Forsgren A, Berglund G, Floren CH. Association between Helicobacter pylori and gastric carcinoma in the city of Malmo, Sweden. A prospective study. Scand J Gastroenterol 1997;32:121521.[Medline]
14 Huang JQ, Sridhar S, Chen Y, Hunt RH. Meta-analysis of the relationship between Helicobacter pylori seropositivity and gastric cancer. Gastroenterology 1998;114:116979.[Medline]
15
Yuan JM, Yu MC, Xu WW, Cockburn M, Gao YT, Ross RK. Helicobacter pylori infection and risk of gastric cancer in Shanghai, China: updated results based upon a locally developed and validated assay and further follow-up of the cohort. Cancer Epidemiol Biomarkers Prev 1999;8:6214.
16 You WC, Zhang L, Gail MH, Li JY, Ma JL, Chang YS, et al. Helicobacter pylori infection, garlic intake and precancerous lesions in a Chinese population at low risk of gastric cancer. Int J Epidemiol 1998;27:9414.[Abstract]
17 Blaser MJ, Chyou PH, Nomura A. Age at establishment of Helicobacter pylori infection and gastric carcinoma, gastric ulcer, and duodenal ulcer risk. Cancer Res 1995;55: 5625.[Abstract]
18 International Agency for Research on Cancer (IARC). Schistosomes, liver flukes and Helicobacter pylori. IARC Monogr Eval Carcinog Risks Hum 1994;61:177240.[Medline]
19 Taylor DN, Blaser MJ. The epidemiology of Helicobacter pylori infection. Epidemiol Rev 1991;13:4259.[Medline]
20 Correa P. Helicobacter pylori and gastric cancer: state of the art. Cancer Epidemiol Biomarkers Prev 1996;5:47781.[Medline]
21 International Agency for Research on Cancer (IARC). Monographs on tobacco smoking. IARC Monogr Eval Carcinog Risks Hum 1985;38:2767.
22 Nomura A, Grove JS, Stemmermann GN, Severson RK. A prospective study of stomach cancer and its relation to diet, cigarettes, and alcohol consumption. Cancer Res 1990;50:62731.[Abstract]
23 Kneller RW, McLaughlin JK, Bjelke E, Schuman LM, Blot WJ, Wacholder S, et al. A cohort study of stomach cancer in a highrisk American population. Cancer 1991;68:6728.[Medline]
24 World Cancer Research Fund/American Institute for Cancer Research. Stomach. In: Food, nutrition and prevention of cancer: a global perspective. Menasha (WI): Banta Book Group; 1997. p. 14875.
25 UK Subgroup of EPC-EURONUT-IM Study Group. Plasma vitamin concentrations in patients with intestinal metaplasia and in controls. Eur J Cancer Prev 1992;1:17786.[Medline]
26 Sobala GM, Pignatelli B, Schorah CJ, Bartsch H, Sanderson M, Dixon MF, et al. Levels of nitrite, nitrate, N-nitroso compounds, ascorbic acid and total bile acids in gastric juice of patients with and without precancerous conditions of the stomach. Carcinogenesis 1991;12:1938.[Abstract]
27 Haenszel W, Correa P, Lopez A, Cuello C, Zarama G, Zavala D, Fontham E. Serum micronutrient levels in relation to gastric pathology. Int J Cancer 1985;36:438.[Medline]
28 U.S. Department of Health and Human Services (DHHS). Hematological and nutritional biochemistry reference data for persons 6 months74 years of age: United States, 19761980. Hyattsville (MD): National Center for Health Statistics, Public Health Service; 1982 (series 11; data from the National Health Survey, No. 232). DHHS Publ No. (PHS)83-1682.
29 Akiba S, Neriishi K, Blot WJ, Kabuto M, Stevens RG, Kato H, et al. Serum ferritin and stomach cancer risk among a Japanese population. Cancer 1991;67:170712.[Medline]
30 Nomura A, Chyou PH, Stemmermann GN. Association of serum ferritin levels with the risk of stomach cancer. Cancer Epidemiol Biomarkers Prev 1992;1:54750.[Abstract]
31 Reed P. Vitamin C, Helicobacter pylori infection and gastric carcinogenesis. Int J Vitam Nutr Res 1999;69:2207.[Medline]
32 Gail MH, You WC, Chang YS, Zhang L, Blot WJ, Brown ML, et al. Design issue and baseline data for a factorial trial of three interventions to reduce the progression of precancerous gastric lesions in Shandong, China. Controlled Clin Trials 1998;19:35269.[Medline]
Manuscript received March 28, 2000; revised August 1, 2000; accepted August 14, 2000.
This article has been cited by other articles in HighWire Press-hosted journals:
![]() |
||||
|
Oxford University Press Privacy Policy and Legal Statement |