Cannabis smoking is suspected to be a risk factor for lung cancer. The KBP-CPHG 2020 study is a prospective study that collected data from all patients with newly diagnosed lung cancer in non-academic hospitals in France in 2020.

We conducted comparative and matched cohort analyses using the dataset, in which cannabis smokers (i.e. participants who self-declared a lifetime intake of ≥20 joints) were compared with tobacco-only smokers. After matching on confounders, we compared age at diagnosis and overall survival.

Among 8999 patients, 314 (3.6%) were cannabis smokers and 7372 were tobacco-only smokers (data missing for 183). Cannabis smokers were younger than tobacco-only smokers at lung cancer diagnosis (mean [± standard deviation] 52.9 [±8.84] versus 67.7 [±9.51] years; p<0.0001), and this difference remained in the paired analysis (matched for histology, sex and cigarette pack-years [±5 pack-years]; n = 298 pairs; median age at diagnosis 53.1 vs 64.8 years; hazard ratio 5.61, 95% CI 4.10–7.68; p<0.0001). Histological type was also different between the two groups, with more cases of adenocarcinoma and large cell neuroendocrine carcinoma among cannabis smokers. Finally, a 1:1 matched analysis controlled for age, sex, stage, histology and cigarette pack-years showed that overall survival was not affected by cannabis smoking (HR 0.90, 95% CI 0.68–1.18; p = 0.44).

We provide a detailed description of lung cancer characteristics among cannabis smokers compared with tobacco-only smokers. Cannabis smoking appeared to be associated with lung cancer diagnosis at an earlier age and was not a prognostic factor for mortality.