Clinical and molecular characteristics of the patients in the liquid biopsy study in mEGFR-NSCLC in a Spanish population (OPH-1).

Abstract

e21515 Background: The liquid biopsy (LB) is an important tool in the diagnostic and follow up of the patients with non-small cell lung cancer (NSCLC) and can provide big information about the mutational variability of the disease during of the treatment. Methods: We conducted a multicenter study with 200 patients with EGFR-mutated NSCLC, treated with first-line TKI therapy. We analyse the ctDNA by dPCR pre-treatment, at 8 weeks, at 7 months and at the progression of the disease (PD). Results: A total of 200 patients (60% women / 40% men) were included. The median of age was 68-year. The never smokers were 56% and 34% ex-smokers. 92% of the cases were adenocarcinomas. According to the stage of the disease, 52% were stage IVB, 38.5% stage IVA and 9.5% unknown. The first-line treatment was afatinib in 47.5%, erlotinib in 21.5% and gefitinib in 31%. According to the type of sensitivity mutation, 61.5% corresponded to Del19, 32% to L858R, 2.5% to G719X and 2.5% to L861Q. At the time of diagnosis, 63% had pulmonary metastatic involvement and 42.5% liver metastasis. At the time of data analysis, 66% of the patients had some progression of the disease (PD) and 37% died. 68% of the patients with Del19 received afatinib, while 20% of the patients with L858R received afatinib, 54.5% erlotinib and 32% gefitinib (p = 0.02). With a median follow-up of 20 months, progression-free survival was 11.8 months, without any differences according to the treatment (p = 0.93). The groups with worse PFS included: the squamous histology (HR 5.7; 95%CI 2.04-15.91, p = 0.001), the G719X mutation (HR 3.36; 95%CI 1.21-9.25, p = 0.019) and the liver metastasis (HR 1.65; 95%CI 1.01-2.68, p = 0.042). The sensitizing mutation was detected in the 80.8% of the patients in the LB by dPCR and the T790M in 2%. However, in the first control only was detectable in 18.5%. At the time of PD, the percentage of detection of T790M raised to 52.3%, and the sensitizing mutation 79.44%. At that moment, patients who developed T790M were mostly never smokers (66%, p = 0.006) and had Del19 (66%). Patients with bone progression developed T790M in 60.4% (p = 0.014) and hepatic 27% (p = 0.012). Conclusions: We concluded that the clinical characteristics of the patients of the OPH study are consistent with the previous reported in the Caucasian population and the subgroups with the worst prognosis include the squamous histology, the G719X mutation and the liver metastasis.