Nab-Paclitaxel Plus Gemcitabine With Concurrent MR-Guided IMRT in Patients With Locally Advanced Pancreatic Cancer

Inclusion Criteria: * Histologically or cytologically confirmed locally advanced adenocarcinoma of the pancreas that is considered unresectable or borderline resectable based on institutional standardized criteria of unresectability or medical inoperability. Patients with and without regional adenopathy are eligible. * Prior systemic chemotherapy allowed. It is anticipated and suggested that most patients enrolled on study will have received a minimum of approximately 2 months of systemic therapy according to routine institutional practices. The patient must also be felt by the treating medical oncologist and radiation oncologist to be a candidate for treatment with gemcitabine/nab-paclitaxel chemoradiotherapy. * At least 18 years of age. * ECOG performance status ≤ 1 * Normal bone marrow and organ function as defined below: * Absolute neutrophil count ≥ 1,000/mcl * Platelets ≥ 100,000/mcl * Hemoglobin ≥ 9.0 g/dL * Total bilirubin ≤ 1.5 x ULN * AST(SGOT)/ALT(SGPT) ≤ 1.5 x IULN * Serum creatinine ≤ 1.5 mg/dL or calculated CrCL\>60mL/min using Cockcroft and Gault formula * Women of childbearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control, abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she must inform her treating physician immediately. * Ability to understand and willingness to sign an IRB approved written informed consent document (or that of legally authorized representative, if applicable). Exclusion Criteria: * Distant metastatic disease, including known brain metastases. * History of prior malignancy is acceptable, but prior radiotherapy to the region of the study cancer that would result in overlap of radiation therapy fields is not allowed. * Currently receiving any other investigational agents. * Major surgery within 4 weeks prior to first study drug administration. * A history of allergic reactions attributed to compounds of similar chemical or biologic composition to gemcitabine or nab-paclitaxel or other agents used in the study. * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Pregnant and/or breastfeeding. Patient must have a negative pregnancy test within 14 days of study entry. * Known HIV-positivity on combination antiretroviral therapy because of the potential for pharmacokinetic interactions with gemcitabine and nab-paclitaxel. In addition, these patients are at increased risk of lethal infections when treated with marrow-suppressive therapy. Appropriate studies will be undertaken in patients receiving combination antiretroviral therapy when indicated.