Dados do Trabalho

Título

Monitoring tumoral circulating DNA (ctDNA) plasma-derived from patients with metastatic colorectal cancer

Introdução

Half of metastatic colorectal cancer (mCRC) harbors oncogenic mutations in KRAS/NRAS that leads to the constitutive activation on MAP kinase pathway, which is one of the mechanisms involved in anti-EGFR therapy resistance. Patients with wild type (WT) KRAS/NRAS tumors are eligible to anti-EGFR treatment while patients with mutated KRAS/NRAS tumors are not. Patients treated with anti-EGFR may show acquired resistance to EGFR inhibitors and one of the mechanisms involved is the emergence of KRAS-activating.

Objetivo

To evaluate the presence of specific-tumor mutations in cell-free DNA in plasma of patients with mCRC under treatment.

Métodos

mCRC patients were divided in 2 groups: 1) tumors with KRAS/NRAS/BRAF activating mutations and 2) wild-type (WT) tumors. Patients of group 2 were divided in two groups: 2A) patients treated with anti-EGFR (Cetuximab) associate with chemotherapy and 2B) patients treated with chemotherapy. The ctDNA analysis was performed using deep-amplicon sequencing using NGS (Next Generation Sequencing) in the Ion S5 platform (Thermo Fischer). To determine the tumor mutational repertory and detecting tumor-specific somatic mutations, in the group 2 (RAS/RAF wild-type) we used a panel containing 409 genes frequently mutated in solid tumors (CCP). Tumor-specific mutation confirmed as negative in patient-leucocyte DNA were tracked on cell-free DNA at personalized manner. Patients of Group 1 and Group 2A had their cell-free DNA tracked using a customized hotspot panel that covers activating mutations in 7 genes, including NRAS, KRAS and BRAF. The hotspot panel was used in the Group 2A for investigating acquired resistance to the anti-EGFR therapy.

Resultados

A total of 53 patients have been included in this study, from which 27 (52.9%) have been classified as group 1 and 26 (50.1%) as group 2. In tumors of Group 1, 81.5% (22/27) had mutations in KRAS, followed by 11.1% in NRAS (3/27), 3.7% in BRAF (1/27) and one case in both KRAS and BRAF 3.7% (1/27). In the group 2, 11 from de 26 patients have been treated with Cetuximab associated with chemotherapy - Group 2A, while the 15 remaining have been treated with chemotherapy only Group 2B. On the group 2, of the 22 tumors analyzed on the 409 genes cancer panel we were able to identify somatic variants tumor-specific in 91% cases (20/22). The cfDNA analysis on both groups have been made via NGS-amplicon multiplex PCR. The results showed that in the baseline samples on the Group 1, 55% (15/27) cases showed presence of ctDNA, while on Group 2 in the baseline samples the detection was positive in 31,5% (6/19) cases. The 15-month monitoring period was divided in two periods, 3- 6 months and 9-15 months. The ctDNA detection, on the first period, was 36% (8/22) for Group 1, 71.4% (5/7) for Group 2A and 55% for Group 2B (5/9). On the second period, the ctDNA were detected in 73% (15/21), 50% (2/4) and 55% (5/9) for the Group 1, 2A and 2B respectively.

Conclusões

Accordingly with the results obtained, we were able to observe that ctDNA baseline was detected more frequently in patients with tumors RAS/RAF-positive, with active MAP pathway. At the end of this study, we would like to assess if ctDNA monitoring can be used as biomarker of prognostic or a complementary tool to anticipate progression.

Palavras-chave

colorectal, liquid biopsy, next generation sequencing

Financiador do resumo

CAPES, PRONON