ECOG Performance Status 3. AE Assessment 4. Medications 5. CBC with differential, platelet count 6. Liver Functions and blood chemistries: Na, K, Cl, CO2, Ca, Mg, PO4, Creatinine, total bilirubin, direct bilirubin, alkaline phosphatase, AST, ALT, LDH 7. Beta-2 Microglobulin, CRP 8. TSH, Free T4, Free T3 9. Evaluation of creatinine clearance 10. Pregnancy test in FOCBP 11. Laboratory Disease Evaluation:  Quantitative serum immunoglobulin levels.  Serum protein electrophoresis (SPEP).  24-hour urine collection to determine creatinine clearance and protein excretion, urine electrophoresis (UPEP).  Immunofixation of urine and serum protein regardless of SPEP and UPEP results.  Serum free light chain ratios (FLC) 12. EKG 13. Nivolumab infusion (Per Section 5.12.1) 14. Vital Signs (including ambulatory O2 sat) per Section 11 15. Study tubes as per Section 10 5.10 Day 15 of Cycles 4-6 (+/- 3 days) 1. History, physical examination, height and weight 2. ECOG Performance Status 3. AE Assessment 4. Medications 5. CBC with differential, platelet count DF/HCC Protocol #: 18-280 Protocol Version Date: 10.17.2020 17 6. Liver Functions and blood chemistries: Na, K, Cl, CO2, Ca, Mg, PO4, Creatinine, total bilirubin, direct bilirubin, alkaline phosphatase, AST, ALT, LDH 7. EKG 8.