Cancer Associated Thrombosis and Isoquercetin (CATIQ)

* This research study is a Phase II/III clinical trial. --The goal of this trial is to evaluate if isoquercetin can prevent blood clots in patients with pancreas, non small cell lung cancer or colorectal cancer. In the Phase II part of this study, the investigators are looking for the dose of isoquercetin to reduce D-dimer and demonstrate safety. * Phase III Endpoint and Treatment Plan * Primary Endpoint for Phase III portion of protocol: Cumulative incidence of VTE. * Following the completion of the phase II portion, enrolled patients will be randomized 1:1 to Arm C (isoquercetin) or Arm D (placebo). The dose for Arm C will be determined after evaluation of the Phase II portion of the trial. The protocol will be amended when the decision is made whether to proceed to Phase III and what dose to use for Arm C. The study will be double-blinded to treatment arm. Lower extremity ultrasound will be performed at 56 days. Baseline D-dimer and correlative labs will be drawn at Day 1 and at 56 days. Patients will be followed for survival after completion of 56 days. * At BIDMC, optional blood draw will be performed at time 0 and 4 hours following the first dose of study drug.