Nivolumab for Recurrent/Metastatic Carcinosarcoma

Inclusion Criteria: 1. Histologically confirmed recurrent/metastatic carcinosarcoma 2. ECOG performance status of 0 to 1 3. ≥ 19 years of age 4. At least 1 prior chemotherapy 5. Patients who have at least 1 measurable disease per the RECIST Guideline Ver. 1.1 as confirmed by imaging within 28 days before randomization 6. Subjects who meet the following criteria: * Absolute neutrophil count (ANC) ≥ 1500 /µ * Platelet count ≥ 75,000/ µL * Serum creatinine \< 1.5 x upper limit of normal (ULN) * AST (SGOT) and ALT (SGPT) \< 3 x upper limit of normal (ULN) (If there is Liver Metastasis \< 5 x upper limit of normal (ULN)) * Total bilirubin \< 1.5 x upper limit of normal (ULN) Exclusion Criteria: 1. More than 4 prior cytotoxic agents 2. Prior treatment with systemic PD-L1-directed therapy 3. Patient who has had chemotherapy, radiotherapy, or biological therapy within 2 weeks prior to entering the study, or who has not recovered from the adverse events due to previous agents administered more than 2 weeks prior to study day 4. Subjects with symptomatic central nervous system (CNS) metastases who are neurologically unstable or have required increasing doses of steroids within the 2 weeks prior to study entry to manage CNS symptoms 5. Patients with multiple primary cancers (with the exception of completely resected basal cell carcinoma, stage I squamous cell carcinoma, carcinoma in situ, intramucosal carcinoma, or superficial bladder cancer, or any other cancer that has not recurred for at least 3 years) 6. History of active non-infectious pneumonitis requiring treatment with steroids, or history or current signs of chronic interstitial lung disease 7. Known active infection