Tissue Pharmacokinetics of Intraoperative Gemcitabine in Resectable Adenocarcinoma of the Pancreas

The Study Drugs: Gemcitabine is a drug used to treat pancreatic cancer. However, there are no studies that show that gemcitabine is able to enter pancreatic cancer cells. Losartan is a drug that lowers blood pressure. It also may increase the amount of gemcitabine that reaches the cancer cells. Participant may be asked to take this drug before participant's surgery. Before Surgery: If participant is found to be eligible and participant agrees to take part in this study, the following tests will be done before participant's surgery: * Participant will have a routine CT (computed tomography) scan and a research MRI (magnetic resonance imaging) of participant's abdomen to check the status of the disease. * Blood (about 3-4 teaspoons) will be drawn for biomarker testing. Participant may be asked to take losartan for 2-4 two to four weeks before participant's surgery (described below). Surgery: Participant's surgery will be performed in the same way as it would be even if participant was not taking part in this study. Participant will sign a separate consent form for surgery. The length of the surgery and the time participant is under anesthesia are not changed by taking part in the study. To measure how much gemcitabine enters pancreas cancer cells, participants who are having their pancreatic cancer removed by surgery will receive an infusion of gemcitabine during the surgery. Some of the pancreatic cancer tissue removed then will be checked to learn if gemcitabine is found in the cancer cells. During surgery, participant will have routine procedures to learn if the disease has spread to other areas. If the disease has spread beyond the pancreas, surgical removal is not possible. If for any reason during the surgery, the surgeon decides that removal of the pancreas is not possible, participant will not receive gemcitabine and participation in this study will end. If there are no signs of spread or other reasons the cancer cannot be removed, the surgeon will begin the process of removal of the disease. Gemcitabine Infusion: Participant will receive an infusion of gemcitabine just before the surgeon begins to remove the cancer. Gemcitabine will be given through an infusion catheter that is placed in the operating room after participant is asleep. The infusion will take over 100 minutes. The infusion catheter is not required for the study but is a standard of care procedure for all participants who are having pancreatic cancer surgery. Participant will sign a separate consent form for the infusion catheter. Losartan Administration: If participant is asked to take losartan, participant will take 1 tablet by mouth every day for up to 4 weeks before participant's surgery. After Week 1, the study staff will tell participant if participant's dose will stay the same or increase, based on any side effects that participant may have. Blood and Tissue Collection: Up to 10 blood samples (about 1 tablespoon each time) will be drawn during surgery starting before the gemcitabine infusion begins and at the end of surgery. The blood samples are used to measure the levels of gemcitabine in participant's blood at different time points. This is called pharmacokinetic (PK) testing. The blood will also be used for biomarker testing. Biomarkers are chemical "markers" in the blood/tissue that may be related to participant's reaction to the study drug. Some of the tumor tissue and normal tissue removed during surgery will be collected to learn if gemcitabine is able to enter the tissue cells and for biomarker testing. Length of Study: Participant's active participation in this study will be over once participant has had surgery and completed the follow-up. The research team will continue to collect information on participant for 30 days after surgery (or until participant is no longer having side effects). Follow-Up: The study team will follow participant's health status for 30 days after surgery to check if participant is having any side effects from gemcitabine. This follow-up will be done daily while participant is in the hospital recovering from the surgery. Follow-up will also occur at the time of a routine clinic visit, or by phone call at least once weekly. These calls should last about 5 minutes each. This is an investigational study. Gemcitabine is FDA approved and commercially available for the treatment of pancreatic cancer. Its use during surgery is investigational. Losartan is FDA approved and commercially available for the treatment of high blood pressure and diabetic nephropathy. It is not approved for the treatment of pancreatic cancer. Up to 40 patients will take part in this study. All will be enrolled at MD Anderson.