Neoadjuvant SBRT With Concomitant Capecitabine in Resectable Pancreatic Cancer

Inclusion Criteria:

* Histologically or cytologically confirmed carcinoma of exocrine pancreatic head amenable to oncological surgical resection per findings on a pancreatic-specific computed tomography (CT) or MRI scan. Tumors of the body that allow a surgical approach similar to pancreatic head tumors are acceptable.
* Must be deemed a surgical candidate by the surgical oncology service.
* Eastern Cooperative Oncology Group (ECOG) performance score of =\< 2
* Signed informed consent document(s)
* Patients with no evidence of regional or distant metastatic disease based on CT scan of the chest/ abdomen/pelvis.
* Absolute neutrophil count (ANC) \>= 1,500 cells/mm3
* Platelet count \>= 100,000 cells/mm3
* Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) =\< 3 times the upper limit of normal
* Total bilirubin =\< 3 times the upper limit of normal if patient had recent biliary stenting, total bilirubin =\< 1.5 times the upper limit of normal if no biliary stenting was done
* Serum creatinine within normal range with a creatinine clearance \>= 30 ml/min
* Neoadjuvant chemotherapy will be permitted prior to the initiation of SBRT radiation therapy on this clinical trial. There must be a minimum of 2 weeks between the completion of any neoadjuvant chemotherapy and the beginning of SBRT radiation therapy. Furthermore, restaging must be done prior to registration to ensure that patients remain resectable.

Exclusion Criteria:

* Patients with primary ampullary, biliary or duodenal cancer would be excluded
* Patients with tumors primarily of the body or tail of the pancreas requiring a distal pancreaticoduodenectomy would be excluded
* (H/ o) Crohn's disease/ ulcerative colitis/ scleroderma
* History of prior allergic reactions attributed to compounds of similar chemical or biologic composition as capecitabine
* History of prior allergic reactions attributed to compounds of CT/ MRI contrast that cannot be managed with appropriate pre-medication prophylaxis and thereby preclude use of baseline/ follow-up or radiation planning imaging
* Any prior external beam radiation will be evaluated to determine radiation field overlaps and appropriateness of protocol radiation, any invasive cancer in the last 5 years (except for a diagnosis of low-risk prostate cancer, treated non-melanoma/melanoma skin cancer, appropriately treated ductal carcinoma in situ or early stage invasive carcinoma of breast and appropriately treated in-situ/early stage cervical/endometrial cancer)
* Pregnant or nursing women; women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) from the point of study entry and for the duration of all active treatments; should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately
* Treatment with a non-approved or investigational drug within 28 days of study treatment
* History of having MRI non-compatible metal (injury- or treatment-related) in the body will be an exclusion criteria specific to the MRI sub-study
* Considering the small size of the PET/MR scanner bore, subjects with known severe claustrophobia or with body habitus not compatible with the bore (\>300lbs, BMI\>40) may also have to be excluded.
* Subjects unable to maintain blood glucose less than 200mg/dl may not be suitable for the PET/MRI substudy.