Marijuana smoking and the risk of head and neck cancer: pooled analysis in the INHANCE consortium.
BACKGROUND
Marijuana contains carcinogens similar to tobacco smoke and has been suggested by relatively small studies to increase the risk of head and neck cancer (HNC). Because tobacco is a major risk factor for HNC, large studies with substantial numbers of never tobacco users could help to clarify whether marijuana smoking is independently associated with HNC risk.


METHODS
We pooled self-reported interview data on marijuana smoking and known HNC risk factors on 4,029 HNC cases and 5,015 controls from five case-control studies within the INHANCE Consortium. Subanalyses were conducted among never tobacco users (493 cases and 1,813 controls) and among individuals who did not consume alcohol or smoke tobacco (237 cases and 887 controls).


RESULTS
The risk of HNC was not elevated by ever marijuana smoking [odds ratio (OR), 0.88; 95% confidence intervals (95% CI), 0.67-1.16], and there was no increasing risk associated with increasing frequency, duration, or cumulative consumption of marijuana smoking. An increased risk of HNC associated with marijuana use was not detected among never tobacco users (OR, 0.93; 95% CI, 0.63-1.37; three studies) nor among individuals who did not drink alcohol and smoke tobacco (OR, 1.06; 95% CI, 0.47-2.38; two studies).


CONCLUSIONS
Our results are consistent with the notion that infrequent marijuana smoking does not confer a risk of these malignancies. Nonetheless, because the prevalence of frequent marijuana smoking was low in most of the contributing studies, we could not rule out a moderately increased risk, particularly among subgroups without exposure to tobacco and alcohol.
Berthiller
Julien
J
Lifestyle, Environment and Cancer Group, IARC, 69008 Lyon, France.
Lee
Yuan-Chin Amy
YC
Boffetta
Paolo
P
Wei
Qingyi
Q
Sturgis
Erich M
EM
Greenland
Sander
S
Morgenstern
Hal
H
Zhang
Zuo-Feng
ZF
Lazarus
Philip
P
Muscat
Joshua
J
Chen
Chu
C
Schwartz
Stephen M
SM
Eluf Neto
José
J
Wünsch Filho
Victor
V
Koifman
Sergio
S
Curado
Maria Paula
MP
Matos
Elena
E
Fernandez
Leticia
L
Menezes
Ana
A
Daudt
Alexander W
AW
Ferro
Gilles
G
Brennan
Paul
P
Hashibe
Mia
M
D000328:Adult; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D005260:Female; D006258:Head and Neck Neoplasms / Q000453:epidemiology*; D006801:Humans; D007407:Interviews as Topic; D007843:Latin America / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D008385:Marijuana Smoking / Q000009:adverse effects* / Q000453:epidemiology; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D014481:United States / Q000453:epidemiology