TAS-102 in Extrapulmonary Neuroendocrine Carcinoma

Inclusion Criteria: * Pathologic confirmation of high grade NEC using WHO criteria as determined by Ki67\>20%, poorly differentiated (G3) characteristics, or \>20 mitotic figures/10 high-power fields. * Unknown primary may be included. Suspected extrapulmonary patients with known lung primary will be excluded. * Prior treatment with a platinum containing regimen * RECIST 1.1 measurable disease * Evidence of stage IV, metastatic disease * Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 2. * Serum albumin ≥2.5 gm/dL. * Expected survival ≥3 months. * Adequate hematologic function as defined by: a) Absolute neutrophil count (ANC) \>1500/mm3; b) Platelets ≥75,000/mm3; c) Hemoglobin \>8 g/dL (in the absence of red blood transfusion). * Adequate liver function, as defined by: a) Serum total bilirubin ≤2.5 x ULN mg/dL. b) ALT (SGPT) and AST (SGOT) ≤5 x upper limit of normal (ULN). * Adequate renal function, as defined by serum creatinine ≤2.0 x ULN, or creatinine clearance ≥30 mL/min * Females of child bearing potential must agree to use contraception to avoid pregnancy throughout the study. Exclusion Criteria: * Women who are pregnant or breastfeeding. * Evidence of low-grade or well-differentiated features as determined by the investigator. * Functional neuroendocrine tumors are excluded. * Known pulmonary primary or small cell lung cancer will be excluded. * Significant or uncontrolled congestive heart failure (CHF), myocardial infarction or significant ventricular arrhythmias within the last six months. * Active infection or antibiotics within 48 hours prior to study enrollment, including unexplained fever (temp \> 38°C). * Other severe and/or uncontrolled medical conditions or other conditions that could affect their participation such as: a) Severe impaired lung functions as defined by spirometry and DLCO that is 50% of the normal predicted value and/or O2 saturation that is 88% or less at rest on room air, b) Uncontrolled diabetes,c) Liver disease such as cirrhosis or severe hepatic impairment, d) Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the integrity of the study. * Taking other investigational or anti-cancer treatments while participating in this study. Concurrent radiotherapy is allowed provided to non-target lesions. If target lesions have received radiation therapy, progression must have been demonstrated prior to enrollment. * Prior or concurrent malignancy, except for the following: a) Adequately treated basal cell or squamous cell skin cancer; b) Cervical carcinoma in situ; c) Adequately treated Stage I or II cancer from which the subject is currently in complete remission; d) Or any other cancer from which the subject has been disease-free for 3 years.