e21560 Background: Tumor growth rate (TGR) signifies percentage change in tumor size per month (%/m). We investigated the association of TGR with outcomes in patients with advanced non-small cell lung cancer (aNSCLC) undergoing anti-PD-1/PD-L1 monotherapy. Methods: We retrospectively reviewed 172 aNSCLC patients treated with anti-PD-1/PD-L1 monotherapy in Sun Yat-Sen University Cancer Center between August 2016 and June 2018. Computed tomography images were reviewed to calculate TGR before treatment (“TGR0”) and upon early treatment (from treatment initiation to the first evaluation; “TGR1”). X-tile software was used to determine cut-off values that maximumly differentiate overall survival (OS). Log-rank tests and Cox regression models were performed for survival analysis. Results: 73 patients with paired TGR0 and TGR1 were included in the testing cohort. The optimal cut-off values of TGR0 and TGR1 were 46.6 %/m and 10.9 %/m, respectively. Patients with higher TGR1 significantly experienced inferior OS versus those with lower TGR1 (HR 2.74, 95% CI 1.34-5.61, P = 0.006). Patients with higher TGR0 tended to have poorer OS, though not statistically significant (HR 1.79, 95% CI 0.84-3.79, P = 0.131). In multivariate analyses, TGR1 remained an independent predictor of OS (HR 2.33, 95% CI 1.12-4.83, P = 0.024). In an external validation cohort (n = 69) enrolling patients with available TGR1 but lacking TGR0 data, TGR1 was also significantly associated with OS (HR 2.73, 95% CI 1.33-5.60, P = 0.006). Conclusions: Higher TGR1 was correlated with inferior outcomes in aNSCLC patients who received anti-PD-1/PD-L1 monotherapy. Larger prospective studies are warranted to identify its added value to RECIST as an early radiological biomarker to predict long-term survival of patients undergoing immunotherapy. [Table: see text]
P1.09-21 Tumor Responses Based on Tumor Growth Rate During PD-1 Inhibitor Therapy in Advanced Non-Small-Cell Lung Cancer Patients
