<sup>68</sup>Ga-FAP-2286 PET of Solid Tumors: Biodistribution, Dosimetry, and Comparison with<sup>18</sup>F-FDG
Brad Kline, Surekha Yadav, Youngho Seo, Robin Cumming Ippisch, Jessa B. Castillo, Rahul Aggarwal, Robin Kate Kelley, Spencer C. Behr, Robert R. Flavell, Courtney Lawhn-Heath, Michelle Melisko, Hope S. Rugo, Victoria Wang, Sue S. Yom, Patrick K. Ha, Fei Jiang, Thomas A. Hope
Abstract
Fibroblast activation protein (FAP), expressed in the tumor microenvironment of a variety of cancers, has become a target of novel PET tracers. The purpose of this report is to evaluate the imaging characteristics of <sup>68</sup>Ga-FAP-2286, present the first—to our knowledge—dosimetry analysis to date, and compare the agent with <sup>18</sup>F-FDG and FAPI compounds. <b>Methods:</b> Patients were administered 219 ± 43 MBq of <sup>68</sup>Ga-FAP-2286 and scanned after 60 min. Uptake was measured in up to 5 lesions per patient and within the kidneys, spleen, liver, and mediastinum (blood pool). Absorbed doses were evaluated using MIM Encore and OLINDA/EXM version 1.1 using the International Commission on Radiological Protection publication 103 tissue weighting factor. <b>Results:</b> Forty-six patients were imaged with <sup>68</sup>Ga-FAP-2286 PET. The highest average uptake was seen in sarcoma, cholangiocarcinoma, and colon cancer. The lowest uptake was found in lung cancer and testicular cancer. The average SUV<sub>max</sub> was significantly higher on <sup>68</sup>Ga-FAP-2286 PET than on <sup>18</sup>F-FDG PET in cholangiocarcinoma (18.2 ± 6.4 vs. 9.1 ± 5.0, <i>P</i> = 0.007), breast cancer (11.1 ± 6.8 vs. 4.1 ± 2.2, <i>P</i> < 0.001), colon cancer (13.8 ± 2.2 vs. 7.6 ± 1.7, <i>P</i> = 0.001), hepatocellular carcinoma (9.3 ± 3.5 vs. 4.7 ± 1.3, <i>P</i> = 0.01), head and neck cancer (11.3 ± 3.5 vs. 7.6 ± 5.5, <i>P</i> = 0.04), and pancreatic adenocarcinoma (7.4 ± 1.8 vs. 3.7 ± 1.0, <i>P</i> = 0.01). The total-body effective dose was estimated at 1.16E−02 mSv/MBq, with the greatest absorbed organ dose in the urinary bladder wall (9.98E−02 mGy/MBq). <b>Conclusion:</b><sup>68</sup>Ga-FAP-2286 biodistribution, dosimetry, and tumor uptake were similar to those of previously reported FAPI compounds. Additionally,<sup>68</sup>Ga-FAP-2286 PET had consistently higher uptake than <sup>18</sup>F-FDG PET. These results are especially promising in the setting of small-volume disease and differentiating tumor from inflammatory uptake.