ABSTRACT
BACKGROUND: Greater height and body mass index (BMI) have been associated with an increased risk of thyroid cancer, particularly papillary carcinoma, the most common and least aggressive subtype. Few studies have evaluated these associations in relation to other, more aggressive histologic types or thyroid cancer-specific mortality. METHODS: This large pooled analysis of 22 prospective studies (833,176 men and 1,260,871 women) investigated thyroid cancer incidence associated with greater height, BMI at baseline and young adulthood, and adulthood BMI gain (difference between young-adult and baseline BMI), overall and separately by sex and histological subtype using multivariable Cox proportional hazards regression models. Associations with thyroid cancer mortality were investigated in a subset of cohorts (578,922 men and 774,373 women) that contributed cause of death information. RESULTS: During follow-up, 2996 incident thyroid cancers and 104 thyroid cancer deaths were identified. All anthropometric factors were positively associated with thyroid cancer incidence: hazard ratios (HR) [confidence intervals (CIs)] for height (per 5 cm) = 1.07 [1.04-1.10], BMI (per 5 kg/m2) = 1.06 [1.02-1.10], waist circumference (per 5 cm) = 1.03 [1.01-1.05], young-adult BMI (per 5 kg/m2) = 1.13 [1.02-1.25], and adulthood BMI gain (per 5 kg/m2) = 1.07 [1.00-1.15]. Associations for baseline BMI and waist circumference were attenuated after mutual adjustment. Baseline BMI was more strongly associated with risk in men compared with women (p = 0.04). Positive associations were observed for papillary, follicular, and anaplastic, but not medullary, thyroid carcinomas. Similar, but stronger, associations were observed for thyroid cancer mortality. CONCLUSION: The results suggest that greater height and excess adiposity throughout adulthood are associated with higher incidence of most major types of thyroid cancer, including the least common but most aggressive form, anaplastic carcinoma, and higher thyroid cancer mortality. Potential underlying biological mechanisms should be explored in future studies.
Subject(s)
Carcinoma/diagnosis , Carcinoma/physiopathology , Thyroid Neoplasms/diagnosis , Thyroid Neoplasms/physiopathology , Adult , Aged , Aged, 80 and over , Anthropometry , Body Mass Index , Carcinoma/mortality , Carcinoma, Papillary , Female , Humans , Male , Middle Aged , Proportional Hazards Models , Prospective Studies , Risk Factors , Smoking , Thyroid Cancer, Papillary , Thyroid Neoplasms/mortality , Waist CircumferenceABSTRACT
OBJECTIVE: Telomeres are required for maintaining genomic integrity and may play a role in carcinogenesis. Some, but not all, epidemiologic studies have found that short telomeres in leukocytes are associated with an increased risk of breast cancer. To further elucidate this potential association, we examined telomere length in relation to breast cancer risk in prospectively collected blood samples from the Sister Study, a cohort of women aged 35-74 years who have a sister with breast cancer. METHODS: We performed a case-cohort analysis comparing incident breast cancer cases (n = 342) with a subcohort (n = 735), randomly selected from 29,026 participants, enrolled by June 1, 2007. Relative telomere length in peripheral blood cells was estimated using a single-tube monochrome multiplex quantitative PCR assay. RESULTS: No association was observed between telomere length and breast cancer risk. Compared with the longest quartile, hazard ratios (HR) associated with the second, third, and the shortest quartile were 0.91 [95% confidence interval (95% CI): 0.62-1.34], 1.11 (95% CI: 0.77-1.60), and 0.93 (95% CI: 0.64-1.35), respectively. Subgroup analyses by menopausal status, invasiveness, or estrogen receptor status of breast cancer did not reveal evidence of association between telomere length in blood cells and subsequent breast cancer risk. CONCLUSIONS: This prospective investigation does not support telomere length in blood cells as a biomarker for breast cancer risk.
