Patient description: The patient is a 41-year-old obese woman coming to the emergency room with abdominal pain and vomiting. The pain that started gradually yesterday is located in the epigastric and periumbilical regions, radiating to her back. She drinks alcohol frequently and does not smoke. She has no history of allergies and uses only multivitamins daily. Her family history is positive for hypertension (her mother). She lives with her husband and has 3 children. The abdomen is tender and soft. Her bowel sounds are normal. Her heart rate is 115/min and blood pressure 110/75 mmHg. The lab studies are remarkable for leukocytosis (19.5), urea of 8.5, high CRP (145), high amylase (1200) and Glucose level of 15. Her abdominal CT scan revealed acute edematous interstitial pancreatitis with enlarged common bile duct and intrahepatic duct confirming gall stone pancreatitis. Her pregnancy test is negative and she is not breastfeeding.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Pancreatic Cancer Histologically-confirmed pancreatic adenocarcinoma or poorly differentiated carcinoma that is metastatic to distant sites Other histologies such as neuroendocrine and acinar cell carcinoma are excluded. Patients with locally advanced, unresectable disease without distant metastases are excluded No prior chemotherapy for locally advanced or metastatic pancreatic cancer Patients are eligible if they received adjuvant treatment after surgical resection with single-agent gemcitabine or gemcitabine plus capecitabine or 5-fluorouracil/leucovorin that was completed >12 months before enrollment. Similarly, adjuvant radiation +/ chemosensitization with 5-fluorouracil, capecitabine, or gemcitabine is allowed if completed >12 months before enrollment Participants must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions) as ≥20 mm with conventional techniques or as ≥10 mm with spiral CT scan, MRI, or calipers by clinical exam. See Section 11 for the evaluation of measurable disease Age greater than or equal to 18 years Patients must have completed any major surgery or open biopsy ≥4 weeks from start of treatment ECOG performance status ≤1 (see Appendix A) Participants must have normal organ and marrow function as defined below  Prior chemotherapy or any other investigational agents for the treatment of locally advanced or metastatic pancreatic cancer Concurrent use of any other anti-cancer therapy, including chemotherapy, targeted therapy, immunotherapy, or biological agents Participants with known brain metastases should be excluded from this clinical trial because of their poor prognosis and because they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events History of allergic reactions attributed to compounds of similar chemical or biologic composition to paricalcitol, gemcitabine or nab-paclitaxel Pre-existing hypercalcemia, defined as baseline serum calcium (corrected for albumin) above the institutional upper limit of normal At the time of trial enrollment, vitamin D containing supplements must be stopped and no vitamin D supplements can be taken while the patient is enrolled to the study due to increased risk for hypercalcemia At the time of trial enrollment, calcium containing supplements must be stopped and no calcium supplements can be taken while the patient is enrolled to the study due to increased risk for hypercalcemia History of symptomatic genitourinary stones (e.g. kidney stones) within the past 12 months History of prior or current synchronous malignancy, except Malignancy that was treated with curative intent and for which there has been no known active disease for >3 years prior to enrollment