This study explores the clinical application of 68Ga-DOTA-CCK-FS PET/CT in detecting cholecystokinin-2 receptor (CCK-2R)-positive tumors, particularly medullary thyroid cancer (MTC) and other malignancies. Led by Prof. Luo Yaping (PUMCH Nuclear Medicine) and Prof. Liu Zhibo (Peking University, radiochemistry expert), the trial will enroll 30-40 patients to compare 68Ga-DOTA-CCK-FS imaging with standard PET/CT (e.g., 18F-FDG or 68Ga-DOTATATE). The novel tracer shows higher tumor uptake and retention in preclinical studies, potentially improving diagnosis and treatment guidance for aggressive, CCK-2R-expressing cancers. The study leverages PUMCH's Class IV Radioactive Drug License for advanced radiopharmaceutical development. Risks are minimal (diagnostic radiation dose only), and participants receive free imaging assessments. Results aim to refine precision diagnostics for MTC and related tumors.

This clinical study investigates the diagnostic potential of 68Ga-DOTA-CCK-FS PET/CT, a novel radiopharmaceutical targeting the cholecystokinin-2 receptor (CCK-2R), in patients with medullary thyroid carcinoma (MTC) and other CCK-2R-expressing tumors. The research is led by Prof. Luo Yaping, Chief Physician at Peking Union Medical College Hospital (PUMCH), in collaboration with Prof. Liu Zhibo, a radiochemistry expert from Peking University. The trial will enroll 30-40 eligible patients with confirmed or suspected MTC (based on histopathology, elevated calcitonin/CEA levels, or MEN2 family history) or other CCK-2R-positive malignancies. Each participant will undergo 68Ga-DOTA-CCK-FS PET/CT, with comparative imaging (either 18F-FDG PET/CT for non-neuroendocrine tumors or 68Ga-DOTATATE PET/CT for neuroendocrine tumors) performed within 2 weeks. The study focuses on evaluating the tracer's sensitivity, specificity, and tumor-targeting efficiency through both visual and quantitative analyses (e.g., SUV measurements). Preclinical data suggest 68Ga-DOTA-CCK-FS offers superior tumor uptake and retention compared to existing probes, potentially enabling earlier detection and better therapeutic stratification for MTC, which often presents with aggressive metastasis and limited treatment options. PUMCH's Class IV Radioactive Drug License allows in-house production of this investigational tracer, addressing unmet clinical needs. Safety monitoring includes tracking minor injection-site reactions or radiation exposure (equivalent to a standard abdominal CT). Participants benefit from free advanced imaging and contribute to refining precision diagnostics for CCK-2R-driven cancers. Results may pave the way for future theranostic applications (e.g., 177Lu-labeled CCK-2R therapy).

Inclusion Criteria:

1. Age not limited (male or female).

2. Diagnosis:Confirmed or suspected medullary thyroid carcinoma (MTC) based on:

   Fine-needle aspiration (FNA) cytology/histopathology, or Elevated serum calcitonin/CEA with thyroid nodule(s), or Clinical/hereditary suspicion (e.g., MEN2 syndrome), or Other histologically confirmed CCK-2R-positive tumors (e.g., neuroendocrine tumors, gastric/ovarian cancers).

3. Performance Status: Life expectancy ≥12 weeks.

4. Contraception: Willingness to use effective birth control (if applicable).

5. Consent: Signed informed consent and compliance with follow-up.

Exclusion Criteria:

1. Severe hepatic/renal dysfunction (e.g., ALT/AST >3×ULN, Cr >2.0 mg/dL).
2. Pregnancy/lactation or planned pregnancy during the study.
3. Inability to lie still for PET/CT (e.g., severe claustrophobia).
4. Concurrent conditions compromising study safety (investigator's judgment).

*Note: CCK-2R positivity may be confirmed via prior immunohistochemistry (if available) or inferred from tumor type (e.g., MTC).*

Due to patient privacy regulations and institutional policies, individual participant data (IPD) from this study will not be publicly available. The data contain sensitive clinical and genetic information that could compromise participant confidentiality. Additionally, Chinese data protection laws and hospital ethical guidelines restrict the open sharing of identifiable medical data.

However, aggregated results (e.g., group-level imaging findings, statistical analyses) will be published in peer-reviewed journals. Researchers may request limited, anonymized datasets for collaborative purposes, subject to approval by the Peking Union Medical College Hospital (PUMCH) Ethics Committee and compliance with data transfer agreements.