Recreational Physical Activity and Differentiated Thyroid Cancer Risk: A Pooled Analysis of Two Case-Control Studies.

PURPOSE: Physical activity has been hypothesized to influence cancer occurrence through several mechanisms. To date, its relation with thyroid cancer risk has been examined in relatively few studies. We pooled 2 case-control studies conducted in Cuba and Eastern France to assess the relationship between self-reported practice of recreational physical activity since childhood and thyroid cancer risk. METHODS: This pooled study included 1,008 cases of differentiated thyroid cancer (DTC) matched with 1,088 controls (age range 9-35 and 17-60 years in the French and Cuban studies, respectively). Risk factors associated with the practice of recreational physical activity were estimated using OR and 95% CI. Logistic regressions were stratified by age class, country, and gender and were adjusted for ethnic group, level of education, number of pregnancies for women, height, BMI, and smoking status. RESULTS: Overall, the risk of thyroid cancer was slightly reduced among subjects who reported recreational physical activity (OR = 0.8; 95% CI 0.5-1.0). The weekly frequency (i.e. h/week) seems to be more relevant than the duration (years). CONCLUSION: Long-term recreational physical activity, practiced since childhood, may reduce the DTC risk. However, the mechanisms whereby the DTC risk decreases are not yet entirely clear.

Common variants at the 9q22.33, 14q13.3 and ATM loci, and risk of differentiated thyroid cancer in the Cuban population.

BACKGROUND: The incidence of differentiated thyroid carcinoma (DTC) in Cuba is low and the contribution of host genetic factors to DTC in this population has not been investigated so far. Our goal was to assess the role of known risk polymorphisms in DTC cases living in Havana. We genotyped five polymorphisms located at the DTC susceptibility loci on chromosome 14q13.3 near NK2 homeobox 1 (NKX2-1), on chromosome 9q22.33 near Forkhead factor E1 (FOXE1) and within the DNA repair gene Ataxia-Telangiectasia Mutated (ATM) in 203 cases and 212 age- and sex- matched controls. Potential interactions between these polymorphisms and other DTC risk factors such as body surface area, body mass index, size, ethnicity, and, for women, the parity were also examined. RESULTS: Significant association with DTC risk was found for rs944289 near NKX2-1 (OR per A allele = 1.6, 95% CI: 1.2-2.1), and three polymorphisms near or within FOXE1, namely rs965513 (OR per A allele = 1.7, 95% CI: 1.2-2.3), rs1867277 in the promoter region of the gene (OR per A allele = 1.5, 95% CI: 1.1-1.9) and the poly-alanine tract expansion polymorphism rs71369530 (OR per Long Allele = 1.8, 95% CI: 1.3-2.5), only the 2 latter remaining significant when correcting for multiple tests. Overall, no association between DTC and the coding SNP D1853N (rs1801516) in ATM (OR per A Allele = 1.1, 95% CI: 0.7-1.7) was seen. Nevertheless women who had 2 or more pregnancies had a 3.5-fold increase in risk of DTC if they carried the A allele (OR 3.5, 95% CI: 3.2-9.8) as compared to 0.8 (OR 0.8, 95% CI: 0.4-1.6) in those who had fewer than 2. CONCLUSIONS: We confirmed in the Cuban population the role of the loci previously associated with DTC susceptibility in European and Japanese populations through genome-wide association studies. Our results on ATM and the number of pregnancies raise interesting questions on the mechanisms by which oestrogens, or other hormones, alter the DNA damage response and DNA repair through the regulation of key effector proteins such as ATM. Due to the small size of our study and to multiple tests, all these results warrant further investigation.

Environmental, lifestyle, and anthropometric risk factors for differentiated thyroid cancer in cuba: a case-control study.

BACKGROUND: The incidence of differentiated thyroid carcinoma (DTC) is low in people of African origin and higher in populations living on islands, but there is no well-established explanation for these differences. Cuba is a multiethnic nation with people of African and Spanish descent. Until now, no study on the risk factors of DTC has focused on the Cuban population. Our aim is to establish the role of environmental and lifestyle factors and to relate anthropometric measurements to the risk of developing DTC in Cuba. METHODS: We performed a case-control study of 203 DTC patients treated in two hospitals in Havana and 212 controls living in the area covered by these hospitals (i.e. parts of Havana and the municipality of Jaruco). Risk factors were analyzed using conditional logistic regression. RESULTS: As has been shown by other studies, we found that non-African ethnicity, never smoking, parity, and high body mass index are risk factors significantly associated with DTC, whereas a history of exposure to ionizing radiation and level of education were not significantly related with disease development. Being rhesus factor-positive, having a personal history of benign thyroid disorder, agricultural occupation, and consumption of artesian well water were also associated with a significantly increased risk of developing DTC. CONCLUSIONS: The original findings reported here concern the risk of DTC that was associated with non-African ethnicity, positive rhesus factor, farming, and drinking water from an artesian well.