Recurrent/Metastatic Olfactory Neuroblastoma: Evaluating the Efficacy and Safety of Nivolumab

Inclusion Criteria: 1. Written informed consent obtained. 2. Age ≥ 18 years. 3. Histologically confirmed olfactory neuroblastoma. 4. Not eligible for curative local therapy (surgery/radiation). 5. Histological confirmation from recurrent/metastatic lesion or PET-CT evidence. 6. Disease progression after prior chemotherapy. 7. ECOG Performance Status 0-1. 8. Expected survival ≥ 3 months. 9. At least one measurable lesion per RECIST v1.1. 10. Adequate organ function; (1) Absolute Neutrophil Count ≥ 1,000/mm³ (2) Hemoglobin ≥ 8.0 g/dL (3) Platelets ≥ 75,000/mm³ (4) Total bilirubin ≤ 1.5×ULN (≤3.0×ULN for constitutional hyperbilirubinemia) (5) AST/ALT ≤ 3×ULN (≤5×ULN with liver metastasis) (6) Serum creatinine ≤ 1.5×ULN or creatinine clearance ≥ 40 mL/min 11. If the participant is female, she agrees to use contraception and refrain from breastfeeding during the treatment and for 5 months after the treatment. If the participant is male, he agrees to use contraception during the treatment and for 7 months after the treatment. Exclusion Criteria: 1. Active progressive multiple primary cancers (synchronous multiple cancers and metachronous multiple cancers with a disease-free interval of 5 years or less. However, lesions equivalent to carcinoma in situ or mucosal cancer that are considered curable by local treatment are not included as multiple primary cancers. Additionally, this may not apply if the attending physician determines that early-stage cancer will not be a prognostic factor.). 2. Has a systemic infection that requires treatment. 3. It has been determined that one is infected with HIV or AIDS-related diseases. 4. Having an active autoimmune disease that required systemic therapy. 5. Having interstitial lung disease. 6. Pregnant or breastfeeding. 7. Any other cases where the attending physician determines that the treatment in this protocol is inappropriate.