Cigarette smoking and risk of non-Hodgkin lymphoma: a pooled analysis from the International Lymphoma Epidemiology Consortium (interlymph).
BACKGROUND
The International Lymphoma Epidemiology Consortium (InterLymph) provides an opportunity to analyze the relationship between cigarette smoking and non-Hodgkin lymphoma with sufficient statistical power to consider non-Hodgkin lymphoma subtype. The results from previous studies of this relationship have been inconsistent, likely due to the small sample sizes that arose from stratification by disease subtype. To clarify the role of cigarette smoking in the etiology of non-Hodgkin lymphoma, we conducted a pooled analysis of original patient data from nine case-control studies of non-Hodgkin lymphoma conducted in the United States, Europe, and Australia.


METHODS
Original data were obtained from each study and uniformly coded. Risk estimates from fixed-effects and two-stage random-effects models were compared to determine the impact of interstudy heterogeneity. Odds ratios (OR) and 95% confidence intervals (95% CI) were derived from unconditional logistic regression models, controlling for study center, age, sex, and race.


RESULTS
In our pooled study population of 6,594 cases and 8,892 controls, smoking was associated with slightly increased risk estimates (OR, 1.07; 95% CI, 1.00-1.15). Stratification by non-Hodgkin lymphoma subtype revealed that the most consistent association between cigarette smoking and non-Hodgkin lymphoma was observed among follicular lymphomas (n = 1452). Compared with nonsmokers, current smokers had a higher OR for follicular lymphoma (1.31; 95% CI, 1.12-1.52) than former smokers (1.06; 95% CI, 0.93-1.22). Current heavy smoking (> or = 36 pack-years) was associated with a 45% increased OR for follicular lymphoma (1.45; 95% CI, 1.15-1.82) compared with nonsmokers.


CONCLUSIONS
Cigarette smoking may increase the risk of developing follicular lymphoma but does not seem to affect risk of the other non-Hodgkin lymphoma subtypes we examined. Future research is needed to determine the biological mechanism responsible for our subtype-specific results.
Morton
Lindsay M
LM
Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Conneticut, USA. mortonli@mail.nih.gov
Hartge
Patricia
P
Holford
Theodore R
TR
Holly
Elizabeth A
EA
Chiu
Brian C H
BC
Vineis
Paolo
P
Stagnaro
Emanuele
E
Willett
Eleanor V
EV
Franceschi
Silvia
S
La Vecchia
Carlo
C
Hughes
Ann Maree
AM
Cozen
Wendy
W
Davis
Scott
S
Severson
Richard K
RK
Bernstein
Leslie
L
Mayne
Susan T
ST
Dee
Fred R
FR
Cerhan
James R
JR
Zheng
Tongzhang
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D004812:Epidemiologic Methods; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000145:classification / Q000453:epidemiology / Q000209:etiology*; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*