ABSTRACT
Immunotherapy has emerged as a very considerable and potent therapeutic method in which immune inhibitors have gained a lot of attention in the curative field of various cancers. Under certain circumstances, when radiotherapy is accompanied by immunotherapy, the efficacy of the therapeutic procedure increases. Irradiated tumor cells follow a pathway called immunogenic cell death, which targets tumor associated antigens. The application of radiolabeled antibodies under the concept of "radioimmunotherapy" (RIT) makes the synergistic targeted therapeutic effect possible. Since antibodies themselves are cytotoxic, they can kill the cells that not only bind but are within the path length of their radiation emissions. RIT can be categorized as a substantial progress in nuclear medicine. The main concept of RIT includes targeting specified tumor-expressing antibodies. The mentioned purpose is achievable by formulation of radiolabeled antibodies, which could be injected intravenously or directly into the tumor, as well as compartmentally into a body cavity such as the peritoneum, pleura, or intrathecal space. RIT has demonstrated very optimistic therapeutic outcomes in radioresistant solid tumors. Wide ranges of efforts are accomplished in order to improve clinical trial accomplishments. In this review, we intend to summarize the performed studies on RIT and their importance in medicine.
ABSTRACT
PURPOSE: The role of fibroblast activation protein inhibitor (FAPI) PET CT scan is not well documented in papillary thyroid cancer (PTC) patients. Patients with radioiodine refractory PTC and high thyroglobulin levels need PET/CT scan which is generally done by 18F FDG. In the current study, the diagnostic performance of 68Ga FAPI and FDG PET/CT scans were compared head to head in patients with radioiodine refractory PTC. METHOD: Fourteen patients with negative whole body Iodine scans and high thyroglobulin levels underwent whole body PET scans with, respectively, 120-310 and 145-370 MBq 68Ga FAPI-46 and 18F FDG. SUVmax of the back ground in the blood pool and liver and the hottest, largest and average neck, mediastinum, lung and bone lesions were calculated and compared. RESULT: Ten patients had at least one active (SUVmax>blood pool) lesion similarly in two scans. The liver and blood pool SUVmax values were 1.25(0.2) and 1.7(0.2) in FAPI and 2.65(0.2) and 2.0(0.2) in FDG PET images, respectively. The difference was significant (p=0.001). Standard SUV of the hottest lesion to liver was above 3 in all FAPI scans but in half of FDG scans. Target lesion number and intensity were similar between two PET studies but in a patient out of 5 pulmonary metastatic patients, pulmonary nodules were negative (SUVmax=0.9) in FDG while positive (SUVmax= 3.8) in FAPI images (i.e. 20% patient upstaged). CONCLUSION: FAPI accumulates in the recurrent and metastatic lesions of patients with Iodine refractory PTC at least as well as FDG with particular privileges as lower injected activity and lower back ground.
