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; Francesco Pepe; Umberto Malapelle; Pasquale Pisapia; Antonella Dal Mas; Daniela Di Giacomo; Giuseppe Calvisi; Giancarlo Troncone; Enrico Ricevuto

doi:10.18632/oncotarget.25180

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

Oncotarget. 2018 May 29;9(41):26279-26290. doi: 10.18632/oncotarget.25180.

Authors

Gemma Bruera^{1

2}, Francesco Pepe³, Umberto Malapelle³, Pasquale Pisapia³, Antonella Dal Mas⁴, Daniela Di Giacomo^{1

2}, Giuseppe Calvisi⁴, Giancarlo Troncone³, Enrico Ricevuto^{1

2}

Affiliations

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.

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 , BRAF₁₅ 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 /BRAF₁₅ wild-type (wt) were 14 (22.2%), mutant (mut) 49 (77.8%): KRAS_2-4 42 (66.7%); NRAS_2-4 11 (16.4%); BRAF₁₅ 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/<5% AF. Mut distribution in KRAS_2-4 /NRAS_2-4 /BRAF₁₅ : 40 (63.5%) >1000×cov/>5% AF, 8 (12.7%) >500×cov/>5% AF, 1 (1.6%) >1000×cov/<5% AF; BRAF₁₅ 1 (1.5%) >500×cov/>5% AF, 4 (6%) >1000×cov/<5% AF. Prevalence of ≥2 mut samples: KRAS_2-4 /NRAS_2-4 /BRAF₁₅ 8 (12.7%); KRAS_2-4 7 (11.1%); NRAS_2-4 5 (7.5%). BRAF₁₅ mutant were all ≥2 mut (7.5%), atypical and associated to KRAS and/or NRAS mut: c.1405 G>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 /BRAF₁₅ , 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 /BRAF₁₅ 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 /BRAF₁₅ genotype, trendy different in triple wt, compared with KRAS_2-4 /NRAS_2-4 /BRAF₁₅ ≥2 mut.

Keywords: 50 genes panel; FIr-B/FOx intensive first line triplet chemotherapy plus bevacizumab; RAS/BRAF mutations; metastatic colorectal cancer; next generation sequencing.