EP1.14-31 Retrospective Study About EGFR Mutations in Lung Cancer: Our Experience in a Spanish Hospital

Abstract

Mutations in the epidermal growth factor receptor (EGFR) tyrosine kinase are observed in approximately 15% of lung adenocarcinomas and usually occur in nonsmokers. The detection of these mutations can be detected either in liquid biopsies or solid tissue biopsies. EGFR mutations are a predictive biomarker for high response and longer survival (both progression-free and overall) with tyrosine kinase inhibitors (TKIs), namely gefitinib, erlotinib, afatinib and osimertinib. We conducted a descriptive and retrospective study including all patients diagnosed with EGFR mutations between January 2007 and September 2018 (both locally advanced and metastatic forms were included). Of the 67 patients, the mean age was 67.2 years. The majority were adenocarcinoma (82.5%), with only 7.9% of squamous and 6.4% large cell carcinoma. The main mutations registered were exon 21 deletion (41%) and exon 19 deletion (4.9%). Only 24.6% had history of smoking. 71.6% of patients present stage IV disease at diagnosis. The main organ involved was the bone (45.8%), followed by the lung (44.1%) and brain (25.4%). Also 13.6% presents pleural, 10.2% liver, 5.1% adrenal and 5.6% lymph node involvement. 84.1% of the patients were treated with TKIs (erlotinib 49.2%, gefitinib 16% and afatinib 19%) while 16% were treated with chemotherapy. With first line treatment, 94.7%presented disease control (41.8% partial response, 41.9% stable disease and 11% complete response). With a mean of 23.6 months, 56.9% of them progressed, mainly involving the lung (28.6%) and the bone (20.6%). Only 9.5% presented brain progression. At the end of the study, 34% had died (overall survival's mean of 27.5 months). In patients with oncogenic driver mutations in EGFR, treatment with TKIs results in a better outcome than standard chemotherapy. This mutation predicts sensitivity to EGFR (our study shows up to 94.7% presents some type of response). Also, this response is longer (23.6 months in our experience) and better tolerated than chemotherapy. Overall survival of these patients is longer too, in our series, round to 27.5 months of overall survival, and mainly related to the tumor stages. More studies will be needed to be able to clarify the prognostic impact of factors such as the smoke status, sex, type of relapse or second line treatment.