PD-008Serial circulating tumor DNA (ctDNA) monitoring to predict response to treatment in metastatic gastrointestinal cancers. (2nd July 2019) - Parikh, A; Kanter, K; Mojtahed, A; Schneider, J; Seventer, E Van; Fish, M; Allen, J; Blaszkowsky, L; Wo, J; Clark, J; Giantonio, B; Goyal, L; et al.