KRAS and Patent ductus arteriosus: We report on the utilization of a novel mutant allele enrichment ctDNA assay in patients with advanced PDA yielding a circulating tumor DNA (ctDNA) KRAS baseline detection rate of 93.7% (95% CI 89.2%–96.7%), outperforming the detection rate of prior reported assays [23, 27, 33–38].