KRAS and neoplasm: None of the somatic tumor mutations present in KRAS, TP53, SMAD4, or CDKN2A were detected in ccfDNA.[10] The absence of ctDNA detection in these common PDAC-associated genes was likely due to a relatively low ccfDNA input – ccfDNA was extracted from only 200 μL of plasma which is one-tenth the volume used in our study for a single technical replicate.