Immune checkpoint inhibitor adoption, timing, and survival in an urban lung cancer cohort: A landmark analysis.

Abstract

e20697 Background: Although immune checkpoint inhibitors (ICIs) improve survival in randomized trials, real-world use is shaped by clinical selection, complicating retrospective survival analyses. We evaluated predictors of ICI receipt and used landmark analyses to assess whether timing of ICI initiation independently impacts survival in a diverse urban lung cancer population. Methods: We conducted a retrospective cohort study with 211 lung cancer patients diagnosed between 2010 and 2025 at a tertiary academic center. Predictors of ICI receipt were assessed using multivariable logistic regression. Overall survival (OS) was evaluated using multivariable Cox proportional hazards models with ICI exposure treated as a time-dependent covariate. Among ICI recipients, exploratory landmark analyses at 90 and 120 days were performed to examine associations between timing of ICI initiation and OS. Results: Seventy-two patients (34.1%) received ICI therapy. Advanced disease stage was the strongest predictor of ICI receipt with Stage IV patients significantly more likely to receive ICIs (OR 7.11, 95% CI 2.86–20.1, p<0.001). Trends toward higher ICI use were observed among older patients (OR 1.03 per year, p=0.066) and Asian patients (OR 3.61, p=0.07). In the time-dependent Cox modeling, ICI receipt was not independently associated with improved OS (HR 0.72, 95% CI 0.39–1.31, p=0.276), whereas advanced stage remained strongly associated with mortality (Stage III HR 2.19, p=0.042; Stage IV HR 3.05, p=0.003). Among ICI recipients, later initiation was associated with improved OS at the 120-day landmark (HR 0.07, p=0.024), with a similar but non-significant trend at 90 days (HR 0.27, p=0.058). Notably, patients initiating ICIs later consistently demonstrated lower baseline disease burden, including fewer Stage IV cases and greater representation of earlier-stage disease. Conclusions: In this real-world urban cohort, ICI adoption was driven primarily by disease stage rather than demographic characteristics. Apparent survival advantages associated with later ICI initiation likely reflect selection bias, as patients with lower disease burden and greater clinical stability survive long enough to initiate therapy later. These findings underscore the importance of accounting for disease severity and time-dependent biases when interpreting observation studies of immunotherapy outcomes. Overall (211) No ICI (139) ICI (72) p-value Age (median [IQR]) 63.00 [57.00, 68.00] 62.00 [57.00, 68.00] 63.50 [58.00, 70.00] 0.207 Male (%) 87 (41.2) 57 (41.0) 30 (41.7) 0.9 Race (%) 0.818 White 62 (29.4) 42 (30.2) 20 (27.8) Black 137 (64.9) 90 (64.7) 47 (65.3) Asian 12 (5.7) 7 (5.0) 5 (6.9) Smoking Status (%) 0.724 Never 29 (13.7) 21 (15.1) 8 (11.1) Former 113 (53.6) 73 (52.5) 40 (55.6) Current 69 (32.7) 45 (32.4) 24 (33.3) Stage (%) <0.001 I 45 (21.3) 38 (27.3) 7 (9.7) II 26 (12.3) 21 (15.1) 5 (6.9) III 56 (26.5) 39 (28.1) 17 (23.6) IV 84 (39.8) 41 (29.5) 43 (59.7) Histology (%) 0.321 NSCLC 179 (84.8) 121 (87.1) 58 (80.6) SCLC 28 (13.3) 15 (10.8) 13 (18.1) Other 4 (1.9) 3 (2.2) 1 (1.4)