Phenethyl Isothiocyanate in Preventing Lung Cancer in Smokers

Inclusion criteria: Initial from phone interview: * Currently smoking 10-45 cigarettes per day for the past year; * Between the ages of 21 and 70 years; * In apparently good physical health with no unstable medical conditions including seizures or cancer; * In stable and good mental health, i.e., currently do not experience unstable or untreated psychiatric diagnosis, including substance abuse, as determined by the DSM-IV criteria, during the past six months; * Not using any other tobacco or nicotine-containing products; * Not on methadone maintenance or stimulants such as ephedra; not a regular user of street drugs and if uses occasionally, willing to abstain during the study; not taking any drugs known to be P4501A6 substrates such as phenobarbital, rifampicin, dexamethasone, ketoconazole, methoxsalen, pilocarpine, or tranylcypromine due to their role in NNK metabolism; * Does not average more than 21 alcoholic drinks per week; * Willing to perform study activities such as having blood sample drawn, urine collection, multiple clinic visits; * For female subjects of child bearing potential, not known to be pregnant or nursing, or planning to become pregnant within next 12 months. For enrollment in the Short-Term Trial: * Subjects who are generally healthy with liver enzyme and blood count values within the ranges shown below based on blood samples drawn at the second screening visit. Specifically: * White blood cells ≥ 3,000/mL * Total bilirubin ≤ 1.5 x upper limits of normal (ULN) * AST (SGOT)/ALT (SGPT) ≤ 2.5 x ULN * BUN and serum creatinine ≤ 1.5 x ULN For enrollment in the Long-Term Trial: * Participated in the short-term trial and invited to participate in the long-term trial; * Possess the GSTM1 null-null genotype; * Smoke 20 or more cigarettes/day with a cumulative smoking history of 20 or more pack-years (one pack-year equals to smoking a pack of cigarettes a day for one year); * Normal liver enzymes based on blood sample drawn during 1 month wash-out; * Determined to be a good candidate for the bronchoscopy procedure by a primary care physician. Exclusion Criteria: * Subjects with uncontrolled hypertension, uncontrolled diabetes mellitus, unstable coronary artery disease, history of cancer other than non-melanoma skin cancer, and pregnant or lactating women will not be eligible.