496P - Higher osimertinib introduction rate achieved by multiple repeated re-biopsy after acquired resistance to first/second generation EGFR-TKIs

Background

Indication for treatment with osimertinib after first/second generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) resistance depends on T790M mutation detected by re-biopsy. REMEDY trial consisting many cases using plasma biopsy revealed osimertinib introduction rate of approximately 25 percent in EGFR-mutant non-small cell lung cancer (NSCLC) patients pretreated with first/second generation EGFR-TKIs. The aim of study is to analyze the data on clinical practice of our hospital, where histological re-biopsy is actively carried out multiple times.

Methods

We retrospectively reviewed our electronic medical records of EGFR-mutant NSCLC patients to examine osimertinib introduction rate and associated outcomes.

Results

Among 95 patients with EGFR-mutant NSCLC, 73 patients received first/second generation EGFR-TKIs. Of 57 progressive disease patients, 50 patients (57/50: 87%) underwent re-biopsy. T790M was detected in 36 patients (36/50: 72%) and osimertinib was introduced in 35 patients (35/50: 70%). Among 36 patients harboring T790M mutation: histological re-biopsy was performed in 21 patients (21/36: 58%); cytology in 12 patients (12/36: 33%); blood biopsy in three patients (3/36: 8.3%). T790M was detected by first re-biopsy in 14 patients (14/36: 39%), and by second or subsequent re-biopsy 22 patients (22/36: 61%). The median overall survival (OS) in osimertinib induction patients was not reached (95% CI, 64.2-not reached) while in non- osimertinib patients median OS was 92.9 months (95% CI, 22.5-not reached) (p = 0.0173). Five year survival rates were 77% and 52%, respectively.

Conclusions

Higher osimertinib introduction rate was achieved by multiple repeated re-biopsy after first/second generation EGFR-TKIs, and its high introduction rate could contribute to better prognosis of EGFR-mutant NSCLC.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Kobe Minimally Invasive Cancer Center.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.