Oncomine panel testing in the clinical management of colorectal cancer: An Irish experience.

212 Background: Early onset colorectal cancer (EOCRC) is defined as colorectal cancer (CRC) in those under the age of 50. It has been hypothesized that the molecular signatures of EOCRC could differ from those of late onset CRC (LOCRC). Next Generation Sequencing (NGS) using the Oncomine Precision Assay is a useful tool to guide treatment decisions based on the presence or absence of oncogene drivers. While not all of these mutations currently influence the clinical management of CRC patients, ongoing research on the function of these genes and the development of new drugs could offer insights into patient prognosis, treatment choices and prediction of therapy resistance. Methods: Of >1500 CRC identified between 2010 and 2024, we investigated the clinical and genetic characteristics of 38 EOCRC and 41 LOCRC cases. All cases were microsatellite stable and staged I-III. NGS was performed with the Ion Torrent Genexus integrated platform using the Oncomine 45-gene Precision Assay panel. DNA hotspot mutations and copy number variations (CNVs) were assessed, followed by the classification of clinically relevant mutations using the genetic variant OncoKB database. Results: There were 38 EOCRC and 41 LOCRC cases. The age range was 27 to 49 and 50 to 91, with median ages of 44 and 72, in the EOCRC and LOCRC groups, respectively. Based on the stratification of NGS mutation levels as per the OncoKB classification, all patients in both groups (100%) had level 1 actionable mutations. NRAS wild type (WT) status was present in 100% of patients in both groups. However, differences were observed in KRAS status: 84% (32/38) of EOCRC were KRAS WT, while only 65% (27/41) of LOCRC were KRAS WT. While 3 % (n=1) of the EOCRC cohort had an ERBB2 amplification, none were detected in the LOCRC group. BRAF V600E mutations were present in 11% (4/38) of EOCRC and 12% (5/41) of LOCRC. Level 4 mutations were detected in 18% (n=7) of EOCRC, all of which were PIK3CA mutations, while these were seen in 24% (n=10) of the LOCRC group, including 9 PIK3CA mutations and 1 FGFR1 mutation. Regarding concurrent mutations, 2 patients in the EOCRC group had two mutations each: one with concurrent KRAS and PIK3CA mutations, and another with concurrent JAK2 and KRAS mutations. The LOCRC group had a higher incidence of concurrent mutations, with 8 patients affected: 6 had concurrent KRAS and PIK3CA mutations, and 2 had concurrent BRAF and PIK3CA mutations. Conclusions: Our study demonstrates that EOCRC have higher KRAS WT status and fewer concurrent mutations compared to LOCRC, who exhibit more frequent KRAS non-G12C oncogenic mutations. It also underscores the importance of routine NGS mutation panel analysis in CRC management. Additionally, identifying specific mutations in patients that relapse can guide targeted therapies, potentially improving outcomes and offering personalized treatment options.