Abstract 3856
Background
Insights into the mechanism of resistance to first generation EGFR-TKIs may provide important information for further patient management, including the choice of second-line treatments. T790M is a gatekeeper mutation of the ATP binding pocket of the EGFR kinase domain and is the most common mechanism of resistance to first-generation EGFR-TKIs. Owing to its biologic relevance in the response of NSCLC to the selective pressure of treatments, the present study investigated in circulating cell-free DNA (cfDNA) if the occurrence of T790M at progression differed among gefitinib, afatinib, and erlotinib.
Methods
This study included patients with NSCLC bearing EGFR activating mutation, and given gefitinib (G), erlotinib (E) or afatinib (A) as first-line treatment. Plasma samples for the analysis of cfDNA were taken at disease progression (PD) and analyzed by a ddPCR using the ddPCR EGFR Mutation Assay. In selected cases, a rebiopsy was performed to confirm the absence of the T790M in negative plasma.
Results
A total of 83 patients were enrolled; 42 patients received G/E and 41 received A. Patients’ characteristics were comparable across the two groups. Median time to progression (TTP) was 14.4 in G/E vs 10.2 months in A group (p = 0.09). Forty-seven out of 83 patients (56.6%) were positive for the T790M in plasma. There was a higher incidence of the T790M in patients who progressed to G/E than in patients treated with A: 33 (79%) vs 14 (34%), respectively (p = 0.0001). To confirm the absence of the T790M, a rebiopsy was feasible in 7 patients of the G/E group and in 23 of the A group. The analysis of the cytological sample confirmed the absence of the T790M, and PI3K mutation was found in both groups in 1 patient (2%). Three patients (7%) had MET amplification in the A group. Afatinib dosage was reduced in 15 patients to 30 mg; T790M was not correlated with the dose reduction, being detectable in 6 patients who needed the reduction and in 8 who received the full standard dose (p = 0.54).
Conclusions
In conclusion, even though gefitinib, erlotinib, and afatinib belong to the same class of EGFR-TKIs, differences in the appearance of resistance mutation are demonstrated in the present study and this finding may have implications in the choice of 2nd-line treatment.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
2182 - Evaluating the prevalence of the expression of PD-L1 in NSCLC specimens with short-duration formalin fixation using IHC 22C3 pharmDx
Presenter: Keiichi Ota
Session: Poster Display session 1
Resources:
Abstract
5255 - [18F]-FDG PET/CT in predicting PD-L1 status in nasopharyngeal carcinoma
Presenter: Liang Zhao
Session: Poster Display session 1
Resources:
Abstract
4910 - Expression of PD-L1 in Chinese Patients with Common Cancers
Presenter: Min Zheng
Session: Poster Display session 1
Resources:
Abstract
4227 - The clearance of EGF by tumor-associated macrophages is suppressed by chemotherapeutic agent cisplatin
Presenter: Irina Larionova
Session: Poster Display session 1
Resources:
Abstract
5222 - VHIO-300 and a thousand one nights, a tale of Precision Medicine
Presenter: Ginevra Caratù
Session: Poster Display session 1
Resources:
Abstract
5668 - Matched Whole-Genome Sequencing and Whole-Exome Sequencing with Circulating Tumor DNA (ctDNA) Analysis are complementary modalities in clinical practice
Presenter: Robin Imperial
Session: Poster Display session 1
Resources:
Abstract
5772 - Exploring the role of genes associated with familial cancer syndromes on the development of multiple primary tumors
Presenter: Atanaska Mitkova
Session: Poster Display session 1
Resources:
Abstract
4784 - Doxorubicin resistance: early and advanced tumors can use two different strategies based on initial and profound abnormalities in microRNA expression signature
Presenter: Volodymyr Halytskiy
Session: Poster Display session 1
Resources:
Abstract
3456 - From tumor transcriptomes to underlying cell type proportions to better predict prognosis and response to treatments
Presenter: Yuna Blum
Session: Poster Display session 1
Resources:
Abstract
4976 - Optimization of automated germline DNA extraction from non-tumoral formalin-fixed paraffin embedded (FFPE) tissues
Presenter: Omar Youssef
Session: Poster Display session 1
Resources:
Abstract