Limited benefit from the addition of immunotherapy to chemotherapy in TKI-refractory EGFR-mutant lung adenocarcinoma.

e21169 Background: The benefit of adding immunotherapy to chemotherapy in EGFR-mutant lung adenocarcinoma (LUAD) with acquired resistance to EGFR tyrosine kinase inhibitors (TKIs) is not fully investigated. This study aimed to explore the outcomes of immunotherapy combinations in such population in a real-world setting. Methods: This retrospective analysis included patients with EGFR-mutant LUAD who progressed on EGFR TKIs and received subsequent therapy with chemotherapy (chemo; n = 84), chemotherapy with immunotherapy (chemoIO; n = 30), chemotherapy plus bevacizumab with or without IO (withBev; n = 42), and IO monotherapy (IO-mono; n = 22). Clinical progression-free survival (cPFS) from the start of the therapy to discontinuation was assessed. Associations of clinical characteristics with cPFS were evaluated using univariable and adjusted Cox regression models. Results: A total of 178 patients (mean age = 62.6; 57.9% females) with a median cPFS (mcPFS) of 4.9 (95% CI: 4.4-5.4) months with 162 (91%) progression events. There was no difference in cPFS between chemoIO vs chemo groups (5.3 months vs 4.8, P = 0.8). Compared to the chemo group, patients who were treated withBev trended towards better PFS (6.1 months vs 4.8; P = 0.3; HR 0.79; 95% CI: 0.52-1.20;), while patients with IO-mono had inferior PFS (2.2 months; P = 0.001; HR 2.22; 95% CI: 1.37-3.59). Patients who were administered one-line of TKI prior to subsequent therapy acquired better PFS when compared to those with multiple prior TKIs (5.2 months vs 4.5; P = 0.011; HR 0.66; 95% CI: 0.48-0.91). The significance remained the same after adjusted by other clinicopathological variables including post-TKI treatment strategies and metastatic status (P = 0.005). Furthermore, among the chemoIO group, patients with PD-L1 expression had better PFS (n = 15, 7.7 months vs 4.5, P = 0.04; HR 0.36; 95% CI: 0.13-0.96) than those without PD-L1 expression (n = 6). However, PD-L1 was not associated with PFS among the patients treated with chemoIO plus bevacizumab. Brain or liver metastases were associated with worse PFS. Conclusions: Immunotherapy adds limited benefit when combined with chemotherapy in TKI-refractory EGFR-mutant LUAD. Chemotherapy +/- bevacizumab are reasonable treatment options for these patients.