The Impact of Dual Cannabis and Tobacco Smoking in Young Patients With Lung Cancer: Results From the Prospective "Environment and Lung Cancer" Study.

[BACKGROUND] The role of cannabis smoking in lung cancer has long been underexplored due to its historical illegality and frequent co-use with tobacco. As cannabis use increases globally, particularly among younger individuals, understanding its impact on lung cancer is critical.

[RESEARCH QUESTION] What is the prevalence of cannabis smoking in young patients with lung cancer? What are the precise characteristics of lung cancer in patients who smoke cannabis?

[STUDY DESIGN AND METHODS] This multicenter prospective study included 150 patients aged ≤ 60 years consecutively diagnosed with primary lung cancer between 2021 and 2023. Smoking behaviors were self-reported and confirmed by hair testing for nicotine, cotinine (a nicotine metabolite), tetrahydrocannabinol, and cannabidiol (cannabis active ingredients). Participants were categorized as patients who smoke cannabis and tobacco (CTSs), patients who smoke exclusively tobacco (TSs), and patients who do not smoke. Clinical features, tumor characteristics, and surgical outcomes were compared between groups.

[RESULTS] Of 148 study patients, 39% were CTSs, 52% were TSs, and 9% were patients who do not smoke. All patients who smoke cannabis also smoked tobacco, with no difference in self-reported pack-years and hair cotinine concentrations compared with TSs. Cannabis use in CTSs was heavy (median duration, 26 years; 4 joints per day). Compared with TSs, CTSs were younger (median age, 53 years vs 56 years; P = .006) and more often reported chest pain at diagnosis (22% vs 8%; P = .03). They also had higher rates of rare and aggressive lung cancers (17% vs 4%; P = .007), more emphysema (64% vs 38%; P = .003), and lower gas diffusion capacity (63% vs 70%; P = .004).

[INTERPRETATION] Our results show that dual cannabis and tobacco smoking is highly prevalent in young patients with lung cancer and is associated with distinct clinical patterns compared with those of TSs, including a higher incidence of emphysema and aggressive tumor types. Further studies are needed to determine the independent effects of cannabis on lung cancer and its potential impact on patient management.