Family history of thyroid cancer and the risk of differentiated thyroid cancer in French polynesia.

BACKGROUND: Differentiated thyroid carcinoma is considered to be the nonhereditary cancer for which familial inheritance is the highest. To date, no familial aggregation analysis of this cancer has been performed in Maohi populations, which exhibit a very high incidence rate. Therefore, we evaluate the risk of differentiated thyroid cancer associated with a family history of thyroid cancer in natives of French Polynesia. METHODS: We investigated thyroid cancer incidence in the first-degree relatives of 225 cases of differentiated thyroid carcinomas diagnosed between 1979 and 2004 in patients born in French Polynesia, and 368 randomly selected population controls matched for sex and age, born and residing in French Polynesia. All but five thyroid cancers declared among relatives were validated. RESULTS: Twenty-four cases declared a family history of thyroid cancer, when compared with 11 controls. Individuals with an affected first-degree relative had a 4.5-fold (95% confidence interval [CI], 1.9-10.6) increased risk of differentiated thyroid cancer. This odds ratio (OR) was not significantly higher when a male first-degree relative was affected (OR, 10.0; 95% CI, 1.3-74.8) compared with a female (OR, 4.0; 95% CI, 1.5-10.3) and was not different for patients who had a nonaggressive thyroid microcarcinoma (OR, 3.5; 95% CI, 0.6-16.4) than those who had a larger cancer (OR, 6.0; 95% CI, 1.8-20.5). This OR was borderline significantly (p, 0.07) higher in Maohis (OR, 11.0; 95% CI, 2.4-48.8) than in individuals of mixed origin (OR, 2.1; 95% CI, 0.8-5.9). CONCLUSION: Our study shows that the familial inheritance of differentiated thyroid cancer is particularly high in Maohi populations.

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

OBJECTIVES: 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. METHODS: Anthropometric factors were analyzed by conditional logistic regression. RESULTS: 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/m2) or obese (BMI > or = 30 kg/m2) 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. CONCLUSION: 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.