Patil, Tejas

9124 Background: Continuing a 1st generation EGFR TKI with chemotherapy upon TKI progression was not shown to be beneficial in the IMPRESS trial. However, the validity of this approach with osimertinib remains under explored. We attempted to characterize the efficacy of continuing osimertinib with chemotherapy in the post-progression setting. Methods: A single-center retrospective review of patients with metastatic EGFR mutant NSCLC who had progressed on osimertinib was performed. Clinical characteristics and treatment outcomes were noted. Progression free survival (PFS), duration of treatment (DOT), overall survival (OS) and rates of intracranial progression were captured. ANOVA or a Fisher exact test were used to identify associations between cohort characteristics and treatment outcomes. Differences in PFS, DOT and OS were assessed using a log-rank test. A Cox proportional hazard model was used to adjust for potential confounders. Results: 73 patients with EGFR mutant NSCLC with post-osimertinib treatment outcomes were identified. Cohort characteristics are summarized in Table. Median duration of follow up was 41 months. Upon progression, osimertinib was discontinued in 34 patients (Cohort A) and continued with next line of therapy in 39 patients (Cohort B). Survival analyses were adjusted for prior lines of therapy, use of platinum doublet chemotherapy, and use of immune checkpoint inhibitors in the post-progression setting. After adjusting for covariates, continuing osimertinib post-progression was associated with an improved PFS (7 vs 4 months; HR 0.58; 95% CI 0.34 – 1.00; p = 0.003) and DOT (7 vs 4 months; HR 0.52; 95% CI 0.31 – 0.87; p = 0.006). There was no difference in OS between Group A and B (52 vs 41 months; HR 0.73; 95% CI 0.43 – 1.24; p = 0.234). Rates of intracranial progression were similar between Group A and B (28% vs 23%; p = 0.649). Conclusions: After adjusting for covariates, continuing osimertinib with chemotherapy in the post-progression setting was associated with a significant difference in PFS and DOT, but with no differences in OS. Continuing osimertinib does not appear to influence the rate of subsequent intracranial progression. Prospective studies are needed to identify the optimal practice pattern.[Table: see text]

9090 Background: The clinicopathologic characteristics and optimal treatment strategies for non-sensitizing EGFR ( ns- EGFR) and HER2 activating mutations in NSCLC remain unclear. Methods: Single-center retrospective study of patients seen at University of Colorado from 2008 – 2018 with stage IV NSCLC was performed. Clinicopathologic features and treatment outcomes of patients with ns-EGFR (Exon 18, Exon 20, L861Q) and HER2 mutations were collected. Best response to TKI was determined (RECIST v1.1). PFS was calculated using Kaplan-Meier method. Results: Among 359 patients, we identified 49 ns-EGFR (36 Exon 20, 10 Exon 18, 3 L861Q) and 28 HER2 mutations (27 Exon 20, 1 gene amplification) detected via NGS (65/77), real-time PCR (9/77), FISH (1/77) and undocumented (2/77). PDL1 > 50% was seen in 44% ns- EGFR and 57% HER2. Adenocarcinoma was the most common histology (97%). Most patients were female (62%), never smokers (63%), and presented with metastatic disease (stage: I 5%, II 4%, III 6%, IV 85%). HER2+ NSCLC demonstrated a tropism for lung metastases (64%) that was significant when compared to EGFR Exon 19, EGFR L858R, ALK, ROS1, and KRAS cohorts (p < 0.001). No differences were found when other metastatic sites were compared. Among evaluable patients, response rates to TKI therapy is shown. Aggregate median PFS on TKI for ns-EGFR and HER2+ NSCLC was 6 months compared to EGFR Exon 19 (15 months; p < 0.01; HR 0.4; CI 0.24 – 0.67) and EGFR L858R (22 months; p < 0.01; HR 0.27 and 0.8; CI 0.14 – 0.54). Aggregate median OS for ns-EGFR and HER2+ NSCLC was 28 months with no differences when compared to EGFR Exon 19 and L858R subgroups. Conclusions: HER2+ NSCLC appears to have a predisposition for lung metastases. Higher DCR was observed with newer generation TKIs, but novel targeted therapeutic approaches are needed as overall outcomes remain poor. [Table: see text]