The objective of the study is to evaluate the diagnostic value of DLL3-targeted PET/CT in patients with suspected or histologically confirmed small cell lung cancer, and to compare with conventional imaging modalities.

This study is designed to investigate DLL3-targeted PET/CT as a noninvasive approach for detecting tumor lesions in patients with suspected or confirmed small cell lung cancer (SCLC).In this research, patients with SCLC or highly suspected recurrence detection underwent contemporaneous DLL3-targeted PET/CT and conventional imaging (such as CT, MRI or 18F-FDG) either for an initial assessment or for metastases or highly suspected recurrence detection. Tumor uptake was quantified by the maximum standardized uptake value (SUVmax). By correlating immunohistochemistry with tumor uptake of the DLL3-targeted tracer, the investigators will explore the feasibility of visualizing tumor DLL3 expression using DLL3-targeted PET. The numbers of positive tumor lesions of conventional imaging and DLL3-targeted PET/CT were recorded by visual interpretation. The diagnostic accuracy of DLL3-targeted was calculated and compared to conventional imaging.

Inclusion Criteria:

• Adult patients (aged 18 years or older);
• Patients with suspected, newly diagnosed, and previously treated small cell lung cancer(supporting evidence may include imaging findings and pathology report);
• Serum ProGRP or NSE level ≥ 3 times the upper limit of normal;
• Patients who were able to provide informed consent (signed by participant, parent or legal representative) and assent according to the guidelines of the Clinical Research Ethics Committee.
• Estimated life expectancy of more than 3 months, as assessed by the investigator, and ability to comply with study procedures and scheduled visits;

Exclusion Criteria:

• The inability or unwillingness of the research participant or legal representative to provide written informed consent.
• Inability to complete PET/CT imaging.