KRAS, NRAS and BRAF mutations detected by next generation sequencing, and differential clinical outcome in metastatic colorectal cancer (MCRC) patients treated with first line FIr-B/FOx adding bevacizumab (BEV) to triplet chemotherapy

// Gemma Bruera 1, 2, * , Francesco Pepe 3, * , Umberto Malapelle 3 , Pasquale Pisapia 3 , Antonella Dal Mas 4 , Daniela Di Giacomo 1, 2 , Giuseppe Calvisi 4 , Giancarlo Troncone 3 and Enrico Ricevuto 1, 2 1 Oncology Territorial Care, S. Salvatore Hospital, Oncology Network ASL1 Abruzzo, University of L'Aquila, L'Aquila, Italy 2 Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, L’Aquila, Italy 3 Department of Public Health, University Federico II, Napoli, Italy 4 Pathology, S. Salvatore Hospital, Oncology Network ASL1 Abruzzo, L'Aquila, Italy * These authors equally contributed to this work Correspondence to: Enrico Ricevuto, email: enrico.ricevuto@univaq.it Keywords: FIr-B/FOx intensive first line triplet chemotherapy plus bevacizumab; metastatic colorectal cancer; next generation sequencing; RAS/BRAF mutations; 50 genes panel Received: October 06, 2017      Accepted: April 05, 2018      Published: May 29, 2018 ABSTRACT Background: First line triplet chemotherapy/BEV significantly improved clinical outcome of MCRC. KRAS/NRAS/BRAF mutations were evaluated by next generation sequencing (NGS) in MCRC patients treated with first line FIr-B/FOx. Methods: KRAS exons 2-4 ( KRAS 2-4 ), NRAS 2-4 , BRAF 15 were evaluated in 67 tumours by ION Torrent platform. Mutation detection criteria: >500×sequence coverage (cov); >1% mutant allelic fraction (AF). Clinical outcomes were compared by log-rank. Results: In 63 samples, KRAS 2-4 / NRAS 2-4 / BRAF 15 wild-type (wt) were 14 (22.2%), mutant (mut) 49 (77.8%): KRAS 2-4 42 (66.7%); NRAS 2-4 11 (16.4%); BRAF 15 5 (7.5%). Sixty mutations were detected, range 1-3 mut: 43 (71.7%) >1000×cov/>5% AF; 9 (15%) >500×cov/>5% AF; 8 (13.3%) >1000×cov/1000×cov/>5% AF, 8 (12.7%) >500×cov/>5% AF, 1 (1.6%) >1000×cov/500×cov/>5% AF, 4 (6%) >1000×cov/A; c.1406 G>C; c.1756 G>A, 2 samples; c.1796 C>T. At 21 months (m) follow-up, clinical outcome wt compared to mut was not significantly different: in KRAS 2-4 / NRAS 2-4 / BRAF 15 , progression-free survival (PFS) 18/12 m, overall survival (OS) 28/22 m; 1/≥2 mutations, PFS 14/11, OS 37/22. PFS was trendy worse in RAS / BRAF wt vs ≥2 mut genes ( P 0.059). Conclusions: Most MCRC harboured KRAS 2-4 / NRAS 2-4 / BRAF 15 mutations by NGS, often multiple and affecting few tumoral clones; 22% were triple wt. Clinical outcome is not significantly affected by KRAS 2-4 / NRAS 2-4 / BRAF 15 genotype, trendy different in triple wt, compared with KRAS 2-4 / NRAS 2-4 / BRAF 15 ≥2 mut.