Phase 3 Study of FOLFIRINOX (mFFX) +/- SBRT in Locally Advanced Pancreatic Cancer

INCLUSION CRITERIA * Histologically-confirmed adenocarcinoma of the pancreas * Determined unresectable by a pancreatic cancer surgeon or a multi-disciplinary or gastrointestinal oncology Tumor Board. * Stable or better disease on re-staging scans * Typically, tumors \< 8.0 cm in greatest axial dimension but final determination of eligibility based upon radiation normal tissue constraints * Eastern Cooperative Oncology Group (ECOG) Performance Status 0, 1, or 2 * Leukocytes (white blood cells, WBC) ≥ 3,000/mL * Absolute neutrophil count (ANC) ≥ 1,500/mL * Platelets ≥ 50,000/mL * Total bilirubin ≤ 1.5 X institutional upper limit of normal (ULN) * Aspartate aminotransferase (AST) / alanine aminotransferase (ALT) ≤ 2.5 X institutional ULN * Creatinine within normal institutional limits * Ability to understand and the willingness to sign an informed consent form * Life expectancy \> 6 months EXCLUSION CRITERIA * Metastatic disease * Prior radiotherapy to the upper abdomen/liver. * Prior chemotherapy for pancreatic cancer, other than up to 4 cycles of modified FOLFIRINOX. * Age \< 18 years * Uncontrolled intercurrent illness including, but not limited to: * Ongoing or active infection (or infections requiring systemic antibiotic treatment) * Symptomatic congestive heart failure * Unstable angina pectoris * Cardiac arrhythmia * Psychiatric illness/social situations that would limit compliance with study requirements. * Any concurrent malignancy other than non-melanoma skin cancer, non-invasive bladder cancer, or carcinoma in situ of the cervix. Patients with a previous malignancy without evidence of disease for \> 5 years will be allowed to enter the trial. * Pregnant or lactating * Women of child-bearing potential who are unwilling or unable to use an acceptable method of birth control (hormonal or barrier method of birth control; abstinence) for duration of the study * Women who are not post-menopausal (as defined in Appendix III) and have a positive urine or serum pregnancy test or refuse to take a pregnancy test * Male subjects who are unwilling or unable to use effective contraception for duration of the study