Thyroid cancer following nuclear tests in French Polynesia

BACKGROUND: Between 1966 and 1974, France conducted 41 atmospheric nuclear tests in Polynesia, but their potential health effects have not previously been investigated. METHODS: In a case-control study, we compared the radiation exposure of almost all the French Polynesians diagnosed with differentiated thyroid carcinoma between 1981 and 2003 (n = 229) to the exposure of 373 French Polynesian control individuals without cancer from the general population. Radiation exposures were estimated using measurements after the nuclear tests, age at time of each test, residential and dietary information. RESULTS: The average thyroid dose before 15 years of age was about 1.8 mGy, and 5% of the cases and 3% of the controls received a dose above 10 mGy. Despite this low level of dose, and after adjusting for ethnic group, level of education, body surface area, family history of thyroid cancer and number of pregnancies for women, we observed an increasing risk (P = 0.04) of thyroid cancer with increasing thyroid dose received before age of 15 years, which remained after excluding non-aggressive differentiated thyroid micro-carcinomas. This increase of risk per unit of thyroid radiation dose was higher (P = 0.03) in women who later experienced four or more pregnancies than among other women. CONCLUSION: The risk estimate is low, but is based on limited exposure data. The release of information on exposure, currently classified, would greatly improve the reliability of the risk estimation. British Journal of Cancer (2010) 103, 1115-1121. doi: 10.1038/sj.bjc.6605862 www.bjcancer.com Published online 31 August 2010 (c) 2010 Cancer Research U

Anthropometric factors in differentiated thyroid cancer in French Polynesia : a case-control study

French Polynesia has one of the world's highest thyroid cancer incidence rates. A case-control study among native residents of French Polynesia included 219 cases of differentiated thyroid cancers diagnosed between 1979 and 2004 (195 women/24 men) matched with 359 population controls (315 women/44 men) on the date of birth. Anthropometric factors were analyzed by conditional logistic regression. The risk of thyroid cancer for women in the highest quartile of body mass index (BMI) before diagnosis and at age 18 was 2.3-fold higher (95% CI, 1.1-4.7 p = 0.04) and 2.3-fold higher (95% CI, 1.2-4.4 p < 0.01), respectively, compared with the lowest. Women who were overweight (BMI = 25-29.9 kg/m(2)) or obese (BMI a parts per thousand yen 30 kg/m(2)) at age 18 and before diagnosis had an increased risk compared with those with a normal lifelong weight (OR = 6.2; 95% CI, 2.5-15.5 p < 0.01). Results for excess weight appeared in similar directions for men, although the number of cases was too small to provide reliable estimates. Height was positively associated with thyroid cancer among men and women. This study shows the role of excess body weight, especially if the onset is during early adulthood, and elevated height in the risk of differentiated thyroid cancer in populations born in French Polynesia

Menstrual and reproductive factors in the risk of differentiated thyroid carcinoma in native women in French Polynesia : a population-based case-control study

French Polynesia has one of the world's highest incidence rates of thyroid cancer. A case-control study among native residents of French Polynesia included 201 women diagnosed with differentiated thyroid cancer before the age of 56 years, between 1981 and 2004, matched to 324 population controls on date of birth. Face-to-face interviews were conducted from 2002 to 2004. Odds ratios were calculated by using conditional logistic regression and were reported in the total group and by ethnic group ("Polynesian" vs. "mixed"). The risk of thyroid cancer increased with natural (odds ratio = 1.9) or artificial (odds ratio = 4.5) menopause compared with that associated with a premenopausal status and with number of births (p for trend = 0.03): odds ratios for one, two, three, four or five, six or seven, and eight or more births were, respectively, 0.90, 1.6, 2.3, 2.2, 2.7, and 1.7 compared with a nulliparous status. Similar results were observed for Polynesian women. No association was observed with irregular menstrual cycles, age at menopause, history of miscarriage or induced abortion, time since last birth, age at and outcome of first pregnancy, or breastfeeding. This study confirms the role of menstrual and reproductive factors in the risk of differentiated thyroid cancer in Pacific island populations