Photoradiation With Verteporfin to Facilitate Immunologic Activity of Pembrolizumab in Unresectable, Locally Advanced or Metastatic Pancreatic Cancer

Inclusion Criteria: * Age ≥ 18 years * Primary tumor histologically or cytologically confirmed (previously biopsied) meta-static, unresectable, or locally advanced pancreatic ductal adenocarcinoma (PDAC), including malignant transformation of a mucinous tumor \[intraductal papillary-mucinous neoplasm (IPMN) or mucinous cystic neoplasm (MCN)\] * NOTE: Primary tumor in pancreas must still be present to be eligible. * Prior treatment for this pancreatic tumor is allowed as follows: * Up to one line (≤1 regimen) of prior therapy is allowed * No prior treatment with FOLFIRINOX * Measurable disease as defined by iRECIST. NOTE: Tumor lesions in previously irradiated area are considered measurable if previous evidence of progression has been found in these lesions * Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1 * Hemoglobin ≥ 9.0 g/dL (obtained ≤ 15 days prior to registration) * White blood cell (WBC) ≥ 2500/mm\^3 (obtained ≤ 15 days prior to registration) * Absolute neutrophil count (ANC) ≥ 1500/mm\^3 (obtained ≤ 15 days prior to registration) * Platelet count ≥ 100,000/mm\^3 (obtained ≤ 15 days prior to registration) * Total bilirubin ≤ 1.5 x upper limit of normal (ULN) (obtained ≤ 15 days prior to registration) * Alanine aminotransferase (ALT) and aspartate transaminase (AST) ≤ 3 x ULN ( ≥ 5 x ULN for patients with liver involvement) (obtained ≤ 15 days prior to registration) * Prothrombin time (PT) / international normalized ratio (INR) / activated partial thromboplastin time (aPTT) ≤ x ULN (obtained ≤ 15 days prior to registration) OR if patient is receiving anticoagulant therapy then INR or aPTT is within target range of therapy * Creatinine ≤ 1.5 x ULN (obtained ≤ 15 days prior to registration) OR calculated creatinine clearance ≥ 50 ml/min using the Cockcroft-Gault formula * Negative pregnancy test done ≤ 8 days prior to registration, for persons of childbearing potential only * Provide written informed consent * Ability to complete questionnaire(s) by themselves or with assistance * Willingness to provide mandatory blood specimens for correlative research * Willingness to provide mandatory tissue specimens for correlative research * Willing to return to enrolling institution for follow-up (during the active monitoring phase of the study) Exclusion Criteria: * Any of the following because this study involves an investigational agent, the genotoxic, mutagenic, and teratogenic effects of which on the developing fetus and newborn are unknown: * Pregnant persons * Nursing persons * Persons of childbearing potential and persons able to father a child who are unwilling to employ adequate contraception * Histology or cytology of pancreatic tumor other than adenocarcinoma * Prior treatment: * Received more than one regimen of treatment for pancreatic cancer * Received prior treatment with FOLFIRINOX * History of immunodeficiency illness or immune suppressive medication including systemic steroid therapy or any other form of immunosuppressive therapy ≤ 7 days prior to registration * Failure to recover from acute, reversible effects of prior therapy regardless of interval since last treatment. * EXCEPTION: Grade 1 peripheral (sensory) neuropathy that has been stable for at least 3 months since completion of prior treatment * Co-morbid systemic illnesses or other severe concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens * Known history of human immunodeficiency virus (HIV) infection * Concurrent active hepatitis B (defined as hepatitis B surface antigen \[HBsAg\] positive and/or detectable hepatitis B virus \[HBV\] deoxyribonucleic acid \[DNA\]) and hepatitis C virus (defined as anti-hepatitis C virus \[HCV\] antibody \[Ab\] positive and detectable HCV ribonucleic acid \[RNA\]) infection * EXCEPTIONS: * For patients with evidence of hepatitis B virus (HBV) infection (HBsAg positive), patients must have completed at least 4 weeks of HBV antiviral therapy and the HBV viral load must be undetectable at the time of registration * Patients with a history of hepatitis C virus (HCV) are eligible if they have an undetectable HCV viral load. Patients must have completed curative anti-viral treatment ≥ 4 weeks prior to registration * NOTE: Patients without symptoms or prior history do not require testing prior to registration * History of unstable angina, new onset angina ≤ 3 months prior to registration, myocardial infarction ≤ 6 months prior to registration, or current congestive heart failure New York Heart Association class III or higher * Uncontrolled intercurrent illness including, but not limited to: * Ongoing or active infection * Current diagnosis or previous history of immune-related (non-infectious) pneumonitis or interstitial lung disease that requires or required steroids * Active autoimmune disease that has required systemic treatment ≤ 2 years prior to registration (i.e., with the use of disease-modifying agents, cortico-steroids, or immunosuppressive drugs) NOTE: Replacement therapy (thyroxine, insulin, or physiologic corticosteroid replacement therapy) is allowed * Any condition requiring systemic treatment with either corticosteroids ( \> 10 mg daily prednisone equivalents) or other immunosuppressive medications. NOTE: Inhaled or topical steroids and adrenal replacement doses \> 10 mg daily prednisone equivalents are permitted in the absence of active autoimmune disease * Symptomatic congestive heart failure * Unstable angina pectoris * Cardiac arrhythmia * Or psychiatric illness/social situations that would limit compliance with study requirements * Other active concurrent malignancy * EXCEPTIONS: Non-melanotic skin cancer, carcinoma-in-situ of the cervix, papillary thyroid cancer, or other in situ cancer that has undergone potentially curative therapy * Receiving any other investigational agent which would be considered as a treatment for the primary neoplasm