Neoadjuvant Chemotherapy and Stereotactic Radiosurgery to Pancreatectomy for Patients With Borderline Resectable Pancreatic Cancer

1\. Chemotherapy : 3 cycles of Gemzar-Abraxane. Nab-Paclitaxel will be delivered at day 1 at the dose of 125mg/m2. Gemcitabine will be delivered at the dose of 1g/m2 at days 1, 8 and 15. Three cycles will be given at 4 weeks intervals. 2\. PET Scanner and Magnetic resonance Imaging within the 10 days of the third chemotherapy cycle 3.Radiation treatment: Stereotactic radiation treatment delivering 30 Gy in 5 fractions over 9 days, according to the ongoing "CYM 6 Spinal CFB1" which was approved by the "Centre National d'Ethique et de Recherches" (CNER) under the Number 20013/1103 (Ongoing Study 3). At first, 4 coïl fiducials will be placed inside and/or around the tumor. 10 days later the imaging preparation procedure will be initiated with a CT Scan and MRI simulation. Both exams will be fused using the fiducials. The Clinical Target Volume (CTV) will include systematically the coeliac trunk until the aorta with a margin of at least 1 cm, the origin of the upper mesenteric vessels until the aorta with at least a margin of 1 cm, the space between the Inferior Cava Vein (ICV) and the aorta in front of the pancreatic region, the space between the portal vein and ICV and finally the right lateral border of the ICV in front of the pancreatic region in case of pancreatic head tumors only. The CTV will also include the tumor mass with a 1 cm margin and the locally positive CT scan or PET scanner nodes with a margin of 1 cm provided it does not overlay the digestive structures that will remain after the surgical resection. Finally all these regions will be linked to make a unique CTV structure. The PTV will be defined as an expansion of 5 mm from the CTV. The doses tolerated to the organs at risk figure in the Ongoing Study 3. Radiation treatment will be initiated 4 weeks after the third chemotherapy cycle. 4\. Surgery : Whipple procedure will be the recommended procedure but will be modified according to the initial tumor location. The extension degree of the resection will remain at the discretion of the surgeon. However all the bowel and duodenum irradiated at the prescription dose will be systematically removed whatever the importance of the surgical resection. Minimal Follow up : 1. Clinical exam every 3 months for 3 years 2. Thoraco-abdominal CT scan at 6, 12, 18, 24, 30 and 36months 3. PET Scanner at 6, 12, 18, 24, 30 and 36months 4. CA 19.9 every 3 months for 3 years