Electron Beam Intraoperative Radiation Therapy Following Chemoradiation in Patients With Pancreatic Cancer With Vascular Involvement

Inclusion Criteria:

* Age ≥ 18 years
* ECOG Performance Status 0-1
* Previous completion of at least three (3) months of EITHER gemcitabine plus nab-paclitaxel OR FOLFIRINOX (5-fluorouracil, oxaliplatin, irinotecan and leucovorin)
* Previous completion of either stereotactic-body radiation therapy (SBRT) (minimum 24 Gy) or external beam irradiation (EBRT) (minimum 45 Gy)
* Participation in any investigational drug study within 4 weeks preceding the start of study treatment is PERMITTED.
* Women of childbearing potential (WOCBP) must use appropriate method(s) of contraception. WOCBP should use an adequate method to avoid pregnancy for 5 months after IORT.
* Men who are sexually active with WOCBP must use any contraceptive method with a failure rate of less than 1% per year. Men receiving nivolumab and who are sexually active with WOCBP will be instructed to adhere to contraception for a period of 7 months after IORT. Women who are not of childbearing potential, i.e., who are postmenopausal or surgically sterile as well as azoospermic men do not require contraception.
* Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

* Evidence of disease progression or distant metastases.
* Pregnant or lactating women
* Treatment for other invasive carcinomas within the last five years who are at greater than 5% risk of recurrence at time of eligibility screening. Carcinoma in-situ and basal cell carcinoma/ squamous cell carcinoma of the skin are allowed.
* Major surgery, excluding laparoscopy, within 4 weeks of the start of study treatment, without complete recovery
* Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
* An active infection requiring systemic therapy
* Other serious medical conditions that the investigator feels might compromise study participation