493P - Is exon 19 deletion different from exon 21 mutation in advanced non-small cell lung cancer: A single centre experience

Abstract

BackgroundEpidermal growth factor receptor (EGFR) deletion of exon 19 and exon 21 mutations are the most common mutations in advanced non-small cell lung cancer (NSCLC) and predict higher sensitivity to EGFR tyrosine kinase inhibitors (TKI). The present study is a retrospective analysis of patients harboring EGFR exon 19 deletions and exon 21 mutations in advanced NSCLC. MethodsData of patients diagnosed with advanced NSCLC patients with EGFR mutations from January 2012 to March 2019 was analysed. EGFR mutation analysis was performed using DNA sequencing by real time polymerase chain reaction method. Exon 19 and exon 21 mutated patients were compared for clinicopathological features and outcomes. ResultsData of 697 patients with lung cancer was retrieved of which 613 patients had advanced NSCLC. A total of 441 patients were evaluated for EGFR mutations and 135 (30.6%) patients were positive for EGFR mutations. The median age at presentation was 57.5 years(range, 30-88). Smoking history was seen in 38 (28.1%) patients and 97 (71.8%) were non smokers. Of these 135 patients with EGFR positivity, 129(95.6%) had adenocarcinoma histology and 6(4.4%) had adenosquamous histology. Exon 19 and exon 21 mutations accounted for 79(58.5%) and 45(33.33%) cases respectively. Mutations in exon 18, exon 20 and double mutations were seen in 2(1.4%), 3(2.2%) and 6(4.4%) patients respectively. Thirty nine (28.8%) patients received initial chemotherapy followed by switch maintenance. Geftinib (82.2%) was the most common TKI used followed by erlotinib (9.6%), Afatinib (4.5%), Osimeritinib (0.8%) and chemotherapy (2.9%). The clinical profile, treatment details and outcomes are tabulated below. The median PFS and OS were 8.9 months (range, 4-42 months) and 18 months (range,4-46 months) respectively.Table493PTableOverall EGFR Positive(n = 135)Exon 19 deletions(n = 79)Exon 21 Mutated (n = 45)P ValueMedian Age (years)57.5 (range, 30-88)55 (range, 35-88)61 (range, 30-80)Sex: Male Female Ratio75 60 1.25:144 35 1.25:125 20 1.25:10.98Smoker: Yes No38 9726 5311 340.32Metastases: Bone B/L lung Pleural effusion Brain Liver67 58 40 22 1039 32 22 20 826 22 13 2 10.36 0.38 0.9 0.03 0.24Rash Grade 1 Grade 2 Grade 337 20 10 723 8 10 513 11 0 20.8Response evaluated Partial response Stable disease Progressive disease111 48 (43.3%) 49 (44.1%) 14 (12.6%)65 27 (41.6%) 31 (47.7%) 7 (10.7%)38 18 (47.4%) 16 (42.1%) 4 (10.5%)0.5 0.6 0.7Median PFS (months)8.99.28.30.8Median OS (months)1818.9170.5 ConclusionsIn patients with EGFR-sensitizing mutations, tyrosine kinase inhibitors offer superior progression free survival and response rates and are well tolerated. Brain metastases at presentation were significantly higher in exon 19 compared to exon 21. No significant differences were observed in median PFS or median OS in EGFR exon 19 deleted or Exon 21 mutated subgroup. Legal entity responsible for the studyDepartment of Medical Oncology, Nizam's Institute of Medical Sciences. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.