Increased fibroblast activation protein expression is positively correlated with the aggressiveness of cancer. Radiolabeled fibroblast activation protein inhibitor therapy, also known as radioligand therapy has become a novel treatment for patients with refractory cancer and disease progression after multiple-lines treatment. However, a major problem in the therapeutic use of 177Lu-DOTA-FAPI has been its short half-life and fast rate of clearance. This study was designed to investigate the efficacy and safety of 177Lu-DOTA-EB-FAPI in patients with various solid tumors who had failed standard therapies.

This investigator-initiated phase II study will include a maximum of 30 subjects with progressive cancer after multiple-line treatment, with an increased radiotracer uptake in tumors on 68Ga-FAPI-46 PET/CT. The fixed dose of 177Lu-DOTA-EB-FAPI is 3.3GBq (90 mCi) per cycle. Treatment is planned for up to 4 cycles, and the time interval between cycles is 6 weeks. The primary endpoint assessed the radiological response (according to RECIST criteria) after completion of radioligand therapy. The secondary endpoints included progression-free survival (PFS), overall survival (OS), dosimetry, and safety of 177Lu-DOTA-EB-FAPI.

Inclusion Criteria:

• Ability to understand and willingness to sign a written informed consent document.
• Age 18 and older.
• Confirmed unresectable or metastatic refractory cancer with measurable disease per RECIST (version 1.1) (i.e. at least 1 lesion > 1 cm or lymph node > 1.5 cm in short axis).
• Progressive disease after multiple-lines treatment.
• Completion of entry into 68Ga-FAPI-46 study and completion of scan. The tumor lesions showing increased radiotracer uptake on 68Ga-FAPI-46 PET/CT (defined as a maximum standardized uptake value ≥10 in more than 50% of metastatic lesions).
• Able to remain motionless for up to 30-60 minutes per scan.

Exclusion Criteria:

• Serum creatinine level >150 μmol/L.
• Hemoglobin level <8.0 g/dL; white-cell count < 2.0×109/L; platelet count < 50×109/L; total bilirubin level >3 times the upper limit of the normal range and serum albumin level <2.0 g/dL.
• Participants with Class 3 or 4 NYHA Congestive Heart Failure.
• Participants with severe allergy, or hypersensitivity to radiographic contrast material.
• Participants with claustrophobia.
• Pregnant or lactating women.