Abstract
Objective: Because the etiology of thyroid cancer is not well described, we conducted a pooled analysis of all published case- control studies, as well as two identified unpublished studies. This paper describes the major characteristics of the 14 studies included in the analysis, as well as the statistical methods employed. Four studies were conducted in the United States (1 each in Washington State, California, Connecticut and Hawaii), 8 in Europe (3 in Sweden, 2 in Norway, 1 in Switzerland, 1 in Italy and 1 in Greece), and 2 in Asia (1 in China and 1 in Japan).
Methods: The original datasets were obtained and restructured in a uniform format. Data on socio-demographic characteristics, anthropometric measures, smoking and alcohol consumption, history of benign thyroid diseases and of other selected medical conditions and treatments, family history of cancer and of benign thyroid conditions, occupation, residence in endemic goitre areas, and dietary habits were analyzed. For women, we also analyzed menstrual and reproductive factors and use of female hormones. Radiotherapy and, in Japan, exposure to the A-bombs were considered as potential confounding factors.
Results: A total of 2,725 cases (2,247 females and 478 males) and 4,776 controls (3,699 females and 1,077 males) were included in this study. Of the cases, 79% were classified as papillary thyroid carcinomas, 14% as follicular, 2% medullary, 1% anaplastic, 1% other histologies, and 3% histological type unknown. Each of the datasets was checked for outliers and consistency. Data were analysed separately by study center, gender, and the two major histologic types (papillary, follicular). Frequency tables and simple statistics were computed for each variable under study. Conditional logistic regression was used to compute odds ratios. For matched studies, the original matching was preserved, whereas, for unmatched ones, five-year age groups were used for matching. Study-specific analyses were computed, and then the data from all the studies were pooled conditioning on study. Heterogeneity between studies, geographic areas and study designs was assessed, and the modifying effect of age was also evaluated.
Similar content being viewed by others
References
Parkin DM, Muir CS, Whelan SL, et al. (1992) Cancer Incidence in Five Continents, Vol. VI. Lyon: IARC Sci Publ, no. 120.
Franceschi S, Boyle P, Maisonneuve P, et al. (1993) The epidemiology of thyroid carcinoma. Crit Rev Oncogenesis 4: 25-52.
Ron E (1996) Epidemiology of thyroid cancer. In: Schottenfeld D, Fraumeni JR Jr., eds. Cancer Epidemiology and Prevention. Oxford: Oxford University Press, pp. 1000-1021.
Ron E, Lubin JH, Shore RE, et al. (1995) Thyroid cancer after exposure to external radiation: a pooled analysis of seven studies. Radiat Res 141: 259-277.
Galanti MR, Ekbom A, Grimelius L, Yuen J (1997) Parental cancer and risk of papillary and follicular thyroid carcinoma. Br J Cancer 75: 451-456.
Preston-Martin S, Bernstein L, Pike MC, Maldonado AA, Henderson BE (1987) Thyroid cancer among young women related to prior thyroid disease and pregnancy history. Int J Cancer 55: 191-195.
Levi F, Franceschi S, Gulie C, Negri E, La Vecchia C (1993) Female thyroid cancer: the role of reproductive and hormonal factors in Switzerland. Oncology 50: 309-315.
McTiernan AM, Weiss NS, Daling JR (1984) Incidence of thyroid cancer in women in relation to previous exposure to radiation therapy and history of thyroid disease. J Natl Cancer Inst 73: 575-581.
McTiernan AM, Weiss NS, Daling JR (1984) Incidence of thyroid cancer in women in relation to reproductive and hormonal factors. Am J Epidemiol 120: 423-435.
McTiernan AM, Weiss NS, Daling JR (1987) Incidence of thyroid cancer in women in relation to known or suspected risk factors for breast cancer. Cancer Res 47: 292-295.
Kolonel LN, Hankin JH, Wilkens LR, Fukunaga FH, Hinds MW (1990) An epidemiological study of thyroid cancer in Hawaii. Cancer Causes Control 1: 223-234.
Goodman MT, Kolonel LN, Wilkens LR (1992) The association of body size, reproductive factors and thyroid cancer. Br J Cancer 66: 1180-1184.
Ron E, Kleinerman RA, Boice JD Jr, et al. (1987) A population-based case-control study of thyroid cancer. J Natl Cancer Inst 79: 1-12.
Preston-Martin S, Jin F, Duda MJ, Mack WJ (1993) A case-control study of thyroid cancer in women under age 55 in Shanghai (People's Republic of China). Cancer Causes Control 4: 431-440.
Wingren G, Hatschek T, Axelson O (1993) Determinants of papillary cancer of the thyroid. Am J Epidemiol 138: 482-491.
Galanti MR, Hansson L, Lund E, et al. (1996) Reproductive history and cigarette smoking as risk factors for thyroid cancer in women: a population-based case-control study. Cancer Epidemiol Biomarkers Prev 5: 425-431.
Galanti MR, Hansson L, Bergstrom R, et al. (1997) Diet and nutrients as risk factors for papillary and follicular thyroid carcinoma. Cancer Causes Control 8: 205-214.
Hallquist A, Hardell L, Degerman A, Boquist L (1993) Occupational exposures and thyroid cancer: results of a case-control study. Eur J Cancer Prev 2: 345-349.
Hallquist A, Hardell L, Degerman A, Boquist L (1994) Thyroid cancer: reproductive factors, previous diseases, drug intake, family history and diet. A case-control study. Eur J Cancer Prev 3: 481-488.
Hallquist A, Hardell L, Degerman A, Wingren G, Boquist L (1994) Medical diagnostic and therapeutic ionizing radiation and the risk for thyroid cancer: a case-control study. Eur J Cancer Prev 3: 259-267.
Glattre E, Haldorsen T, Berg JP, Stensvold I, Solvoll K (1993) Norwegian case-control study testing the hypothesis that seafood increases the risk of thyroid cancer. Cancer Causes Control 4: 11-16.
D'Avanzo B, La Vecchia C, Franceschi S, Negri E, Talamini R (1995) History of thyroid diseases and subsequent thyroid cancer risk. Cancer Epidemiol Biomarkers Prev 4: 193-199.
Linos A, Linos DA, Vgotza N, Souvatzoglou A, Koutras DA (1989) Does coffee consumption protect against thyroid disease? Acta Chir Scand 155: 317-320.
Breslow NE, Day NE (1980) Statistical Methods in Cancer Research: Vol. 1. The Analysis of Case-Control Studies. Lyon: IARC Sci Publ, no. 32.
Whittemore AS, Harris R, Itnyre J, Halpern J and the Collaborative Ovarian Cancer Group (1992) Characteristics relating to ovarian cancer risk: collaborative analysis of 12 US case-control studies. I. Methods. Am J Epidemiol 136: 1175-1183.
Collaborative Group on Hormonal Factors on Breast Cancer (1996) Breast cancer and hormonal contraceptives. Lancet 347: 1713-1727.
Clayton D (1991) The Eurodem collaborative re-analysis of case-control studies of Alzheimer's disease: some methodological considerations. Int J Epidemiol 20(Suppl. 2): S62-S64.
Beral V (1995) The practice of meta-analysis: discussion. Meta-analysis of observational studies: a case study of work in progress. J Clin Epidemiol 48: 165-166.
Spitzer WO (1995) The challenge of meta-analysis. J Clin Epidemiol 48: 1-4.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Negri, E., Ron, E., Franceschi, S. et al. A pooled analysis of case-control studies of thyroid cancer¶ I. Methods. Cancer Causes Control 10, 131–142 (1999). https://doi.org/10.1023/A:1008851613024
Issue Date:
DOI: https://doi.org/10.1023/A:1008851613024