Comparing DLL3 PET/CT to Standard Scans in Neuroendocrine Cancer

Inclusion Criteria: * Age ≥ 18 and ≤ 80 years at the time of signing the informed consent form, male or female. * Histologically or cytologically confirmed neuroendocrine neoplasms (NENs), including but not limited to small cell lung cancer (SCLC), neuroendocrine prostate cancer (NEPC), gastroenteropancreatic neuroendocrine tumors (GEP-NENs), or other NEN subtypes. * Patients with strong clinical and radiological suspicion of NENs based on imaging (CT/MRI/conventional PET/CT) and clinical presentation. * At least 2 evaluable metastatic lesions (multiple metastases) confirmed by conventional imaging (CT/MRI/PET/CT). * Eastern Cooperative Oncology Group (ECOG) performance status 0-2. Life expectancy \> 3 months. * Voluntarily agrees to participate and provides written informed consent. * Females of childbearing potential and male participants agree to use reliable contraceptive methods for 6 months after the last study drug administration. * Willing and able to comply with scheduled visits, diagnostic procedures, clinical laboratory tests, and other study procedures. Exclusion Criteria: * Known severe immediate-type hypersensitivity or anaphylactic reaction to DLL3-targeted tracers, nanobody proteins, chelators, buffer components, or excipients. * Pregnant or breastfeeding women. * Estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73m². * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 3 × upper limit of normal (ULN). * Total bilirubin \> 1.5 × ULN. * Inability to tolerate or cooperate with PET/CT imaging procedures, including but not limited to: severe claustrophobia, inability to remain supine and still for at least 30 minutes, or inability to establish adequate intravenous access. * Received chemotherapy, biological therapy, endocrine therapy, molecular targeted therapy, or investigational drug therapy within 4 weeks prior to enrollment. * Currently participating in another interventional clinical trial. * Prior exposure to any DLL3-targeted therapeutic agent (e.g., Tarlatamab, bispecific T-cell engagers, or DLL3-targeted radioimmunotherapy) or DLL3-targeted radiotracer. * Prior radionuclide therapy or diagnostic scan with an interval of less than 10 physical half-lives of the administered radionuclide prior to study tracer administration. * History of any other malignancy within 5 years prior to screening, except for adequately treated non-melanoma skin cancer, carcinoma in situ of the cervix, or other malignancies with negligible risk of recurrence in the investigator's opinion. * Clinically significant abnormalities on physical examination, electrocardiogram (ECG), or clinical laboratory tests during screening that, in the investigator's opinion, may compromise safety or study compliance. * Any other condition that, in the investigator's opinion, makes the patient unsuitable for study participation (e.g., severe psychiatric disorders, substance abuse, poor compliance).