[Cannabis and cancer].

Several publications have recently suggested a relationship between cannabis use and certain types of cancer. We gathered information on the latest findings on the subject. A manual and computerized bibliographic search on cannabis and cancer was conducted. In users under 40 years of age, cannabis is suspected to increase the risk of squamous-cell carcinoma of the upper aerodigestive tract, particularly of the tongue and larynx, and possibly of lung. Other tumours being suspected are non-lymphoblastic acute leukaemia and astrocytoma. In head and neck cancer, carcinogenicity was observed for regular (i.e. more than once a day for years) cannabis smokers. Moreover, cannabis increases the risk of head and neck cancer in a dose-response manner for frequency and duration of use. Interaction was observed with cigarette smoking and alcohol use. Delta9-THC seems to have a specific carcinogenic effect different from that of the pyrolysis products. Epidemiological studies are needed as soon as possible to provide data on the European and French situation. Information on the possible risks of a regular use of cannabis should be a priority.