Sin Nee Tan1, Aishah Ibrahim1, Megat Razeem Abdul Razak1, Muhammad Naimmuddin Abdul Azih2, Soon Hin How2
1Hospital Tengku Ampuan Afzan, Kuantan, Malaysia
2Kulliyyah of Medicine, International Islamic University Malaysia, Pahang, Malaysia
Introduction
In Malaysia, 80% of lung cancer patients are non-small cell lung cancer (NSCLC) and about 45% are epidermal growth factor receptor (EGFR) mutation (EGFRm+). The use of third generation EGFR tyrosine kinase inhibitors (TKIs) osimertinib is regard as standard second line after failed first or second generation EGFR TKI in EGFRm+ NSCLC patients upon disease progression when blood or tissue T790M positive.
Objective
To describe the proportion of EGFRm+ NSCLC patients who were started on lower dose of osimertinib as second line treatment, the median of progression free survival (PSF) and overall survival (OS).
Methodology
This is a single center retrospective study. All patients with advanced stage EGFRm+ NSCLC who started on lower dose of osimertinib upon disease progression from 1st of June 2018 to 30th June 2021. The median PFS, resistant mechanism upon progressive disease (PD), and median OS were assessed.
Results
Of the 28 patients with EGFRm+ NCSLS were treated with osimertinib upon disease progressed, 10 were treated with below recommended dose of osimertinib. All patient received first or second generation EGFR TKIs as first-line therapy. Among the 10 patients, only 1 patient underwent re-biopsy upon disease progression with the result of tissue T790M positive. Another 9 patients underwent blood T790M testing, 8 were positive blood T790M, 1 were negative blood T790M. For lower dose osimertinib regime in this study, half of the patient on osimertinib 40mg EOD while another half were on 40mg OD according to patient’s affordability. As high as 90% of patient had partial response, 10% were stable disease. The overall median PFS was 11 months and median OS was 28 months.
Conclusion
This is the first real-world experience on lower dose of osimertinib as second line treatment in EGFRm+ advanced NSCLC population within a cost-restrictive setting impacts the overall outcomes.