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Pilot study of plasma KRAS as a prognostic biomarker in localized pancreas ductal adenocarcinoma (PDAC).

294 Background: Validated predictive and prognostic biomarkers are needed in PDAC. Such biomarkers could predict response and resistance early in treatment. As 95% of PDAC harbor KRAS mutations (mKRAS), plasma mKRAS has utility as a biomarker. We explored the prognostic value of mKRAS in a PDAC cohort at Memorial Sloan Kettering. Methods: 10 mL of whole blood was collected at diagnosis of localized PDAC and early interval CT scan (approx. 8 weeks). DNA was extracted with QIAamp DNA kits (Qiagen, Valencia, CA). Single locus, if tissue KRAS known, or multiplex (G12A, G12C, G12D, G12R, G12S, G12V, G13D) digital droplet PCR (ddPCR) was performed with QX200 (BioRad, Hercules, CA) ddPCR system. Disease status was determined by radiographic, CA19-9 and clinical evaluation. Results: N = 18 enrolled (median age: 65 [range 34-85]). Median time between baseline (B) and interval (I) blood was 2.53 months (range 0.9-6). One had locally recurrent disease, 2 AJCC stage IIa, 1 IIb and 14 III. Three had tissue KRAS G12D mutation, 6 G12V and 9 unknown. Eight had gemcitabine-based treatment, 10 5-FU-based and 5 radiation. See table. mKRAS and CA19-9 at B were not associated with progression free survival (PFS) or overall survival (OS). mKRAS detection at I was associated with shorter PFS/OS (P < 0.01), but CA19-9 was not. mKRAS change from B to I was also associated with PFS/OS. For every 1 copy/mL increase in the change of mKRAS from B to I, the risk of death or progression/death increased by nearly 2 fold after controlling for baseline value (p = 0.01 for OS, p = 0.03 for PFS). Four patients, all undetectable mKRAS at I, went to surgery; 2/4 resected. Conclusions: In this pilot, 59% of localized PDAC patients had detectable mKRAS at B. mKRAS detection at I and change from B to I were associated with PFS/OS supporting that mKRAS early in treatment may be a useful prognostic and predictive marker in localized PDAC. We have initiated a large prospective trial to evaluate the predictive and prognostic potential of plasma mKRAS in advanced PDAC. [Table: see text]