Paricalcitol Addition to Chemotherapy in Patients With Previously Untreated Metastatic Pancreatic Ductal Adenocarcinoma

Pancreatic cancer is the fourth-highest cancer killer worldwide with an overall 5 year survival of about 8%. The only potentially curative procedure, surgical excision, is feasible in a minority of patients, but even in these patients the majority (\~80%) die within 5 years. This study aims to see if adding paricalcitol (a vitamin D analogue) to chemotherapy can slow down tumour growth in patients with previously untreated metastatic pancreatic cancer. Studies have shown vitamin D can change the pancreatic tumour microenvironment from an immunologically suppressive (tumour growth promoting) to an immunologically hostile one, slowing down tumour growth in this way. Patients with pancreatic cancer that has spread to other organs and who have adequate hepatic and renal function are eligible. Participants will receive chemotherapy (paclitaxel and gemcitabine, with or without cisplatin). On development of stable disease or disease progression, paricalcitol will be added to the chemotherapy regimen and participants will continue on this treatment until their cancer stops responding to treatment. After that participants will be followed up 3 monthly for the collection of disease status and survival data. Participants will be asked to donate tumour and blood samples to allow the research team to look at the effects on the tumour biology.