Simultaneous identification of 36 mutations in KRAS codons 61and 146, BRAF , NRAS , and PIK3CA in a single reaction by multiplex assay kit

摘要

Background Retrospective analyses in the West suggest that mutations in KRAS codons 61 and 146, BRAF , NRAS , and PIK3CA are negative predictive factors for cetuximab treatment in colorectal cancer patients. We developed a novel multiplex kit detecting 36 mutations in KRAS codons 61 and 146, BRAF , NRAS , and PIK3CA using Luminex (xMAP) assay in a single reaction. Methods Tumor samples and clinical data from Asian colorectal cancer patients treated with cetuximab were collected. We investigated KRAS, BRAF , NRAS , and PIK3CA mutations using both the multiplex kit and direct sequencing methods, and evaluated the concordance between the 2 methods. Objective response, progression-free survival (PFS), and overall survival (OS) were also evaluated according to mutational status. Results In total, 82 of 83 samples (78 surgically resected specimens and 5 biopsy specimens) were analyzed using both methods. All multiplex assays were performed using 50?ng of template DNA. The concordance rate between the methods was 100%. Overall, 49 (59.8%) patients had all wild-type tumors, 21 (25.6%) had tumors harboring KRAS codon 12 or 13 mutations, and 12 (14.6%) had tumors harboring KRAS codon 61, KRAS codon 146, BRAF , NRAS , or PIK3CA mutations. The response rates in these patient groups were 38.8%, 4.8%, and 0%, respectively. Median PFS in these groups was 6.1?months (95% confidence interval (CI): 3.1–9.2), 2.7?months (1.2–4.2), and 1.6?months (1.5–1.7); median OS was 13.8?months (9.2–18.4), 8.2?months (5.7–10.7), and 6.3?months (1.3–11.3), respectively. Statistically significant differences in both PFS and OS were found between patients with all wild-type tumors and those with KRAS codon 61, KRAS codon 146, BRAF , NRAS , or PIK3CA mutations (PFS: 95% CI, 0.11–0.44; P Conclusions Our newly developed multiplex kit is practical and feasible for investigation of a range of sample types. Moreover, mutations in KRAS codon 61, KRAS codon 146, BRAF , NRAS , or PIK3CA detected in Asian patients were not predictive of clinical benefits from cetuximab treatment, similar to the result obtained in European studies.