Nintedanib in Treating Patients With Locally Advanced or Metastatic Neuroendocrine Tumors

Inclusion Criteria: * Patient must be on a stable dose of octreotide (Sandostatin®) long-acting release (LAR) or lanreotide for 3 months prior to study enrollment * Patient must have histologically or cytologically confirmed well differentiated or moderately differentiated (low grade or intermediate grade) neuroendocrine tumor that is locally advanced or metastatic and not of pancreatic origin * Measurable disease determined by computed tomography (CT) or magnetic resonance imaging (MRI) * Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 * Life expectancy greater than 3 months * Leukocytes \>= 3,000/uL * Absolute neutrophil count \>= 1,500/uL * Total bilirubin =\< 2 mg/dL * Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) =\< 1.5 x upper limit of normal (ULN) and bilirubin =\< ULN for patients without liver metastases * AST/ALT =\< 2.5 x ULN and bilirubin =\< ULN for patients with liver metastases * Patients with Gilbert syndrome and bilirubin \< 2 x ULN and normal AST/ALT * Creatinine =\< 1.5 mg/dl * Prior treatment will be permitted including surgery (\>= 4 weeks), cytotoxic chemotherapy (maximum of 2 prior regimens); radiation, interferon, targeted growth factors (\>= 4 weeks); and prior treatment with octreotide, will be allowed * Ability to swallow and retain oral medication * Participants of child-bearing potential (both male and female) must agree to use adequate contraceptive methods (e.g., hormonal or barrier method of birth…