Baseline tumor size and survival outcomes in lung cancer patients treated with immune checkpoint inhibitors

Background: Baseline tumor size (BTS) was recently indicated as prognostic of overall survival (OS) in patients advanced melanoma treated with pembrolizumab. We review the association between BTS and OS/progression-free survival (PFS) in patients with a diagnosis of advanced non–small-cell lung cancer (NSCLC) treated with atezolizumab. Methods: Data from 1,461 patients with a diagnosis of advanced NSCLC enrolled in the OAK, POPLAR, BIRCH, and FIR trials and treated with atezolizumab were pooled and analyzed. Using Cox proportional hazards regression, we modeled the association between baseline SLD and survival outcomes. Multivariable analyses were adjusted for pretreatment ECOG PS, age, sex, race, smoking status, histology, count of prior treatments, PDL1 expression, serum LDH levels, and the presence of liver, lung, or brain lesions. Results: On univariable and multivariable analysis, baseline sum of the longest diameters of target lesions (SLD) was identified as significantly associated with OS (hazard ratio [95% confidence interval] per decimeter: 1.64 [1.41–1.91], P < .001) and PFS (1.21 [1.07–1.38], P = .003). Median OS were 16 months versus 10 months for baseline SLD < median, versus baseline SLD ≥ median, respectively. Median PFS were 4 months versus 3 months, respectively. Conclusions: Large BTS was identified as an independent prognostic factor of worse OS and PFS, raising the need to evaluate atezolizumab as an earlier NSCLC treatment in future trials.