A pooled analysis of case-control studies of thyroid cancer: cigarette smoking and consumption of alcohol, coffee, and tea.
OBJECTIVE
To analyze the role of smoking, alcohol, coffee and tea in relation to thyroid cancer, we conducted a pooled analysis of 14 case-control studies conducted in the United States, Europe, and Asia.


METHODS
The sample consisted of 2725 thyroid cancer cases (2247 females, 478 males) and 4776 controls (3699 females, 1077 males). Conditional logistic regression with stratification on study, age at diagnosis, and gender was used to compute odds ratios and 95% confidence intervals.


RESULTS
Thyroid cancer risk was reduced in persons who had ever smoked. The relationship was more pronounced in current smokers (OR = 0.6, 95% CI = 0.6-0.7) than former smokers (OR = 0.9, 95% CI = 0.8-1.1). There were significant trends of reduced risk with greater duration and frequency of smoking. For consumption of wine and beer, there was a significant trend of decreasing thyroid cancer risk (p = 0.02) that was not maintained after adjustment for current smoking (p = 0.12). Thyroid cancer risk was not associated with consumption of coffee or tea. These findings were consistent in both gender-specific and histology-specific (papillary and follicular) analyses.


CONCLUSIONS
Pooled analyses of these geographically diverse case-control data indicate a reduced thyroid cancer risk associated with current smoking. A reduced risk associated with alcohol was eliminated after adjustment for smoking, and caffeinated beverages did not alter thyroid cancer risk.
Mack
Wendy J
WJ
Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
Preston-Martin
Susan
S
Dal Maso
Luigino
L
Galanti
Rosaria
R
Xiang
Min
M
Franceschi
Silvia
S
Hallquist
Arne
A
Jin
Fan
F
Kolonel
Laurence
L
La Vecchia
Carlo
C
Levi
Fabio
F
Linos
Athena
A
Lund
Eiliv
E
McTiernan
Anne
A
Mabuchi
Kiyohiko
K
Negri
Eva
E
Wingren
Gun
G
Ron
Elaine
E
D000428:Alcohol Drinking; D016022:Case-Control Studies; D003069:Coffee; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D012907:Smoking; D013662:Tea; D013964:Thyroid Neoplasms / Q000209:etiology*
D003069:Coffee; D013662:Tea