Abstract
Background: Routine analysis of KRAS, NRAS, BRAF V600 mutations, as well as MSI and HER2 guides treatment selection in colorectal cancer (CRC). Recent findings from the PRESSING and PARADIGM trials have demonstrated that the negative hyperselection of patients based on the results of comprehensive genomic profiling results in better treatment outcomes following anti-EGFR therapy. Study objective: The study aimed to retrospectively analyze the occurrence of alterations associated with potential resistance in samples from CRC patients treated with anti-EGFR therapy.Materials and methods: Patients with confirmed left-sided CRC treated with anti-EGFR therapy due to the lack of RAS / BRAFV600 mutations as per routine PCR were included in the study. FFPE samples were analyzed via NGS (Solo-test Atlas Pro, 38 genes, MSI). Samples determined as RAS / BRAFV600positive by NGS were validated with PCR.Results: A total of 111 samples were analyzed via NGS. A total of 172 alterations in 17 genes were found; alterations in any of the genes covered by the panel were found in 96 (86.5 %) samples. The variant allele frequency ranged 1.3–93.0 %. NGS identified 29 (26.1 %) samples with KRAS (n = 24), NRAS (n = 3) or BRAF p. V600E (n = 4) mutations. Confirmatory PCR testing of 16 RAS / BRAF p. V600E-positive samples resulted in 100 % agreement with NGS. Among RAS / BRAFV600negative samples, 10 (9 %) samples harbored other alterations (ERBB2 amplification, n = 3; PIK3CA, n = 2; MSI, n = 1; BRAF class II mutation, n = 1; ERBB3, n = 1). A total of 11 samples harbored more than 1 alterations associated with potential resistance. BRAF class II / III mutations were found in 4 samples, PIK3CA mutations — in 17 (15.3 %) samples (of those, 5 samples harbored mutations in exon 21).Conclusions: The results of this retrospective analysis demonstrate that a high frequency of false-positive routine PCR results may lead to incorrect indication of anti-EGFR therapy in ~ 26 % cases. Analysis of alterations beyond RAS / BRAFV600 might identify an additional 9 % of patients whose tumors are potentially resistant to anti-EGFR therapy.
Published Version
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