Real-world outcomes of pemetrexed-platinum chemotherapy plus osimertinib after progression on first-line osimertinib in advanced EGFR-mutated NSCLC.

Abstract

e20531 Background: First-line pemetrexed-platinum chemotherapy + osimertinib (Pem-Plat-Osi) improves progression free survival as compared to osimertinib (Osi) alone in advanced epidermal growth factor (EGFR)-mutated non-small cell lung cancer (NSCLC). However, many patients are hesitant to commence chemotherapy upfront. We describe the outcomes of patients who receive Pem-Plat-Osi after progression on first-line Osi in 2 tertiary cancer centres. Methods: Patients with advanced EGFR-mutated (ex19del/L858R) NSCLC who had Pem-Plat-Osi between 1/7/2018-30/9/2023 after progression on first-line Osi at National Cancer Centre Singapore and Chinese University of Hong Kong were identified. Primary endpoints were time to treatment failure (TTF) and overall survival (OS) by Kaplan-Meier. Results: A total of 60 patients were included. Median age at diagnosis was 62, 53% (32/60) were male and 77% (46/60) were never smokers. Ex19del comprised 57% (34/60) and L858R 43% (26/60). Baseline central nervous system (CNS) metastases were present in 67% (40/60). Median TTF1 on Osi was 12 months (m) and median time to initiation of Pem-Plat-Osi was 41 days (d) (range 0-652) after progression on Osi. CNS failure occurred in 10 patients (16.7%). Partial response (PR) to Pem-Plat-Osi was achieved as best response in 45% (27/60), stable disease in 37% (22/60) and progressive disease in 18% (11/60). Three of 4 patients with CNS PD on Osi who did not undergo brain radiotherapy achieved PR/SD to Pem-Plat-Osi. At median follow up of 31m, median TTF2 on Pem-Plat-Osi was 6m, median TTF1+TTF2 was 20m and median OS was 34m. Comparing ex19del and L858R, there was no significant difference in median TTF1 (10m vs 12m, p=0.63), TTF1+TTF2 (19m vs 21m, p=0.50) and OS (34m vs 36m, p=0.40). Median TTF1+TTF2 (19m vs 20m, p=0.84) and OS (31m vs 36m, p=0.68) were similar in patients with or without baseline CNS metastases. There was no significant difference in TTF2 comparing patients who had TTF1<12m versus TTF1≥12m (both median 6m, p=0.56). Patients who started Pem-Plat-Osi within 20d of progression on Osi had significantly longer TTF2 as compared to patients who started after 20d (median 8m versus 5 months, hazard ratio [HR] 0.46, 95% confidence interval [CI] 0.23-0.89, p=0.016) although there was no significant difference in OS (median 31m versus 34 months, p=0.35). Achieving PR was predictive of superior TTF2 (median 8m vs 5m, HR 0.46, 95% CI 0.26-0.84, p=0.005) but not OS (median 36m vs 32m, p=0.45). Conclusions: Our real-world data supports the efficacy of Pem-Plat-Osi after progression on first line Osi, including among L858R subtype and patients with baseline CNS metastases. Chemotherapy initiation within 20d of Osi progression and achieving PR were significantly associated with superior TTF2. Sequential approach of adding chemotherapy upon osimertinib failure is a plausible treatment option.