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.
Lifestyle, Environment and Cancer Group, IARC, 69008 Lyon, France.
Julien
J
Berthiller
Yuan-Chin Amy
YC
Lee
Paolo
P
Boffetta
Qingyi
Q
Wei
Erich M
EM
Sturgis
Sander
S
Greenland
Hal
H
Morgenstern
Zuo-Feng
ZF
Zhang
Philip
P
Lazarus
Joshua
J
Muscat
Chu
C
Chen
Stephen M
SM
Schwartz
José
J
Eluf Neto
Victor
V
Wünsch Filho
Sergio
S
Koifman
Maria Paula
MP
Curado
Elena
E
Matos
Leticia
L
Fernandez
Ana
A
Menezes
Alexander W
AW
Daudt
Gilles
G
Ferro
Paul
P
Brennan
Mia
M
Hashibe
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