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

Objectives: First-line pemetrexed-platinum chemotherapy + osimertinib(Pem-Plat-Osi) improves progression-free survival as compared to osimertinib 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 outcomes to Pem-Plat-Osi after first-line osimertinib failure.

Materials And 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 osimertinib at National Cancer Centre Singapore, Prince of Wales Hospital and Chinese University of Hong Kong were identified. Key endpoints were time to treatment failure (TTF) and overall survival (OS).

Results: A total of 60 patients were included. Median age at diagnosis was 62, 53.3 % (32/60) were male and 76.7 % (46/60) were never smokers. Ex19del comprised 56.7 % (34/60) and L858R 43.3 % (26/60). Baseline central nervous system (CNS) metastases were present in 66.7 % (40/60). Median TTF on osimertinib (TTF1) was 14.4 months(m) and median time to initiation of Pem-Plat-Osi was 41 days(d) (range 0-652) after progression on osimertinib. Partial response (PR) or stable disease to Pem-Plat-Osi was achieved in 81.7 %(49/60). Intracranial disease control was achieved in 90.6 % (29/32) of patients with measurable CNS metastases, including those who did not undergo brain radiotherapy. At median follow up of 31.2 m, median TTF on Pem-Plat-Osi (TTF2) was 6.6 m. Median TTF1 + TTF2 was 23.4 m and median OS was 34.2 m. Survival outcomes were similar comparing ex19del and L858R (median TTF1 + TTF2 21.8 m vs 23.5 m, p = 0.90; median OS 34.2 m vs 36.8 m, p = 0.37) and in patients without/with baseline CNS metastases (median TTF1 + TTF2 21.8 m vs 23.4 m, p = 0.44; median OS 36.2 m vs 31.9 m, p = 0.65). TTF1 duration was not significantly associated with TTF2 (p = 0.76). Patients who started Pem-Plat-Osi within 20d of progression on osimertinib had significantly longer TTF2 as compared to patients who started after 20d (median 8.4 m versus 6.0 months, p = 0.03), which remained statistically significant on multivariable analysis.

Conclusions: Our real-world data supports the efficacy of Pem-Plat-Osi after progression on first-line osimertinib, including L858R and baseline CNS metastases. Chemotherapy initiation within 20d of Osi progression was predictive of superior TTF2.