Effect of smoking status on risk of mortality for patients with lung cancer treated with immunotherapy.

e20648 Background: Immune checkpoint inhibitors have become a mainstay of treatment for lung cancer. However, their effectiveness varies, and is strongly influenced by patient characteristics. Smoking is the most important etiologic factor for lung cancer, and is expected to be associated with a high tumor mutational burden, which may in turn influence immunotherapy response. However, the extent to which smoking status modifies the benefit of immunotherapy in real-world populations is not well established. Methods: We identified 43,437 cases of invasive lung cancer with documentation of smoking status from the California Cancer Registry 2010-2021. Immunotherapy was documented as given or not given. Smoking status was defined as never, current or former. Cox regression was used to assess the unadjusted risk of mortality associated with immunotherapy and after adjusting for age, sex, race/ethnicity, stage, socio-economic status (SES), Charlson Comorbidity Index and insurance status. Analyses were conducted separately for current and former and never smokers. Results: Smoking status was documented for 43,347 cases (never = 15.887, current = 27,056, and former = 404). There were 4,014 cases treated with immunotherapy. The unadjusted risk of mortality for patients treated with immunotherapy was increased in non-smokers whereas immunotherapy reduced the risk of mortality in current and former smokers. After adjustment, all patients had a reduced risk of mortality, but current and former smokers had a higher risk reduction than non-smokers. Conclusions: Smoking modifies the effect of immunotherapy in patients with lung cancer, and our data suggests patients who currently or formerly smoked may derive a greater benefit from immunotherapy. This will need careful patient messaging as we continue public efforts towards smoking cessation. Unadjusted and adjusted* hazard ratios and 95% confidence intervals for immunotherapy. Unadjusted Adjusted* HR (95%CI) HR (95%CI) Never smokers 1.35 (1.26, 1.45) 0.76 (0.70, 0.82) Current or former smoker 0.86 (0.82, 0.91) 0.52 (0.49, 0.55) *Adjusting for age, sex, race/ethnicity, stage, SES, Charlson Comorbidity Index and insurance status.