Agena bioscience5/31/2023 ![]() There was no recurrence in any patient with negative ctDNA post-surgery. Post-operative ctDNA samples were available for 13 patients and residual mutations were detected in 10 patients (77%), 3 of whom (30%) had recurrence at median follow up of 20.1 months. ![]() NRAS and PIK3CA mutations were identified in the ctDNA of 2/3 (67%) and 1/2 (50%) patients. Mutations in NRAS and PIK3CA were identified in 3/27 (11%) and 2/27 (7%) of patients, respectively. 10 patients had a KRAS mutation in their baseline ctDNA that was not detected in their biopsy, with a median MAF of 0.3% (range 0.1-1.3%). This significantly decreased over treatment (0.15% week 3 RT, 0.35% final week RT, 0.1% prior to surgery) (p < 0.05). The median KRAS mutant allele frequency (MAF) in baseline ctDNA samples was 0.9% (range 0.1-2%). Identical mutations were found in baseline ctDNA of 11/15 patients (73%). ResultsĪt least one mutation was identified in 67% (18/27) of baseline biopsy samples. The UltraSEEK™ Colon Panel (Agena Bioscience) was used to track 107 hotspot mutations in serial ctDNA samples. ![]() DNA from baseline biopsy samples was genotyped for 86 hotspot mutations in BRAF, EGFR, KRAS, NRAS and PIK3CA using the iPLEX™ HS Colon Panel on the MassARRAY® System (Agena Bioscience). MethodsĢ7 LARC patients who were enrolled on the CTRIAL-IE (ICORG) 12-38 TRI-LARC clinical trial (NCT02151019) and received NACRT prior to surgery, had samples for ctDNA analysis taken at baseline pre-NACRT, during week 3 of radiotherapy (RT), during the final week of RT, prior to surgery, and 3-12 months post-surgery. We assessed whether detection and analysis of plasma ctDNA could help monitor tumor evolution during neoadjuvant chemoradiotherapy (NACRT) treatment for LARC. There is limited information on the feasibility and clinical potential of ctDNA analysis in non-metastatic rectal cancer.
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