Novel Somatic Genetic Variants as Predictors of Resistance to EGFR-Targeted Therapies in Metastatic Colorectal Cancer Patients

Background: About 40% of RAS/BRAF wild-type metastatic colorectal cancer (mCRC) patients undergoing anti-EGFR-based therapy have poor outcomes. Treatment failure is not only associated with poorer prognosis but higher healthcare costs. Our aim was to identify novel somatic genetic variants in the primary tumor and assess their effect on anti-EGFR response. Patients and Methods: Tumor (somatic) and blood (germline) DNA samples were obtained from two well-defined cohorts of mCRC patients, those sensitive and those resistant to EGFR blockade. Genetic variant screening of 43 EGFR-related genes was performed using targeted next-generation sequencing (NGS). Relevant clinical data were collected through chart review to assess genetic results. Results: Among 61 patients, 38 were sensitive and 23 were resistant to treatment. We identified eight somatic variants that predicted non-response. Three were located in insulin-related genes (I668N and E1218K in IGF1R, T1156M in IRS2) and three in genes belonging to the LRIG family (T152T in LRIG1, S697L in LRIG2 and V812M in LRIG3). The remaining two variants were found in NRAS (G115Efs*46) and PDGFRA (T301T). We did not identify any somatic variants related to good response. Conclusions: This study provides evidence that novel somatic genetic variants along the EGFR-triggered pathway could modulate the response to anti-EGFR drugs in mCRC patients. It also highlights the influence of insulin-related genes and LRIG genes on anti-EGFR efficacy. Our findings could help characterize patients who are resistant to anti-EGFR blockade despite harboring RAS/BRAF wild-type tumors.

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Clinicopathological and genomic characteristics of POLE-mutated colorectal cancer in a Chinese population.

Journal of Clinical Oncology ◽

10.1200/jco.2021.39.15_suppl.e15531 ◽

2021 ◽

Vol 39 (15_suppl) ◽

pp. e15531-e15531

Author(s):

Xuhui Zhang ◽

Xicheng Wang ◽

Ying Xin ◽

Yuezong Bai ◽

Jian Li ◽

...

Keyword(s):

Colorectal Cancer ◽

Chinese Population ◽

Gene Mutations ◽

Metastatic Colon Cancer ◽

Wild Type ◽

Tumor Mutational Burden ◽

Dna Replication And Repair ◽

Colorectal Cancer Patients ◽

Next Generation Sequencing Ngs ◽

Generation Sequencing

e15531 Background: DNA polymerase ε (POLE) is essential for proofreading and fidelity in DNA replication and repair. Previous studies found that mutation in POLE associated with higher tumor mutational burden (TMB), which is an approved biomarker for immunotherpy in solid tumors. However, the clinicopathological and mutational analyses of POLE-mutated colorectal cancer in a large Chinese population have not yet been reported. Methods: Hybrid capture-based next-generation sequencing (NGS) were performed in 4628 samples of colorectal tumors and matched normal pairs in a CAP/CLIA-approved laboratory (3DMed). NGS testing for gene mutations, TMB and MSI was implemented. Results: Of 4628 colorectal cancer patients, POLE mutations were observed in 67 patients (1.45%). A total of 11 different POLE mutations were identified, mostly associated with exonucleas domain. P286R(32,0.69%), V411L(13,0.28%), A456P(7,0.15%), S459F(3,0.06%) and S297F(3,0.06%) were the most frequently mutated sites of POLE. We also detected 1 V758L and 1 W1130R mutation outside the exonuclease domain in separate cases. Among the 4628 patients, 2157 patients were detectable for TMB by NGS panel, including 2128 POLE wild type and 29 POLE mutation patients. The TMB of patients with POLE mutations was significantly higher than that in wide type POLE tumors (mean TMB 252.3 vs 13.4 muts/Mb, P ＜0.0001). All the 29 POLE-mutated patients were TMB-H (≥10 muts/Mb) and 28 of them were MSS. A MSS patient with metastatic colon cancer harboring A456P POLE mutation responsed well to the immunotherpy and achieved a partial response. Conclusions: Our results realved a remarkable positive correlation between POLE mutation and TMB level in a Chinese colorectal cancer population, which suggests POLE gene will be a promising biomarker of immunotherpy for MSS colorectal tumor.[Table: see text]

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