Real-World Experience of First-Line Osimertinib in EGFR Mutated Non-Small Cell Lung Cancers from a Tertiary Cancer...

Osimertinib is approved in the first line in patients with mutations in the sensitive gene epidermal growth factor receptor (EGFR) mutation. There is lack of real-world evidence to illustrate the effectiveness and safety of osimertinib that can reflect the current medical practice especially in resource-constrained setting. A total of 129 patients with histology-proven metastatic non-small cell lung cancer with EGFR mutation registered at Tata Memorial Hospital between from March 2018 and May 2023 were analyzed. The parameters studied included demographics, outcomes, safety analysis, and secondary mutations. Most common EGFR mutation was exon 19 deletion 58.9% followed by EGFR exon 21 L858R 39.5% and others 1.5%. The overall median progression-free survival was 21.9 months (95% confidence interval [CI]: 16.0-58.1) and median overall survival was 31 months (95% CI: 17.8-45). The median duration of response was 21.3 months (95% CI: 17.1-25.5). Of 129 patients, 77.5% had partial response (PR), 10.1% had stable disease (SD), and 6.2% patients had progressive disease (PD) as the first best response with overall disease control rate was 87.2%. In patients with baseline central nervous system disease, 8.9% had complete response, 75.5% had PR and 8.9% had SD, and 2.2% had PD as best response. The overall intracranial response rate was 84.4% and disease control was 93.3%. Skin toxicities (27.1%) and gastrointestinal toxicities (17%) were most frequently observed toxicities. Overall, 63 patients had progression of disease on osimertinib. Subsequently, 58.7% ( n  = 37) patients received second line of therapy and 27% ( n  = 17) patients received third line of therapy. Platinum-based combination chemotherapy was the most common subsequent treatment after progression on osimertinib. Repeat biopsy was done in 33 patients (52.3%) and next-generation sequencing was done in 30 patients (47.6%). The most common resistance alteration detected was TP53 in 30% cases followed by mesenchymal epithelial transition (MET) amplification which was seen in 20% cases. Our study confirms similar efficacy and safety of osimertinib as first-line treatment of mutated non-small cell lung cancer in real-world setting irrespective of the type of common EGFR mutation and similar intracranial activity as well.