The correlation between FDG and FBPA uptakes in malignant tumors by PET/CT

1423 Objectives For Boron neutron capture therapy (BNCT), 10B-boronophenylalanine (BPA) has been used as a boron delivery agent to tumor cell. To evaluate BPA levels by positron emission tomography (PET), 18F-fluoro-boronophenylalanine (FBPA) has been developed and synthesized from 1991. However, FBPA-PET study is not suitable for screening use because of the limitations of FBPA-synthesis from 18F2 gas such as low radio-yielding, low specific activity, and high cost. In this study, we demonstrated the correlation between 18F-fluorodeoxyglucose (FDG) and FBPA uptakes in patients with various malignant tumors to consider whether FDG-PET can be used as a screening for BNCT-applicable patients. Methods Twenty five patients with malignant tumor were set as the target, and inspected both FDG-PET/CT and FBPA-PET/CT within 2 weeks in our hospital. Whole-body PET/CT studies of FDG and FBPA were performed with scan protocol of 3 min/bed acquisition at 1h post injection. Region of interest (ROI) were placed within tumor and normal tissue. Maximum of standardized uptake value (SUV) and tumor versus normal tissue uptake ratio (TNR) were calculated and compared between FDG and FBPA-PET/CT. Internal dosimetry for FBPA was also calculated from sequential whole-body PET/CT data of 1, 2, and 4 h post injection. Results The SUV of FBPA in tumor ranged 1.8to 11.7 (average,4.5±2.8), whereas that of FDG ranged 1.9 to 12.4 (average, 8.5±5.5). Between FDG and FBPA, SUV in the tumor and TNR showed acceptable correlation (r=0.86, and 0.85, respectively). In some cases of malignant melanoma, SUVs of FBPA were relatively higher than expected SUVs of FDG. Internal dosimetry of FBPA was calculated to be 1.2 x 10-2 mSv/MBq, whereas that of FDG was reported to be 1.9 x 10-2 mSv/MBq. Conclusions The accumulation of FBPA in tumor was correlated with that of FDG. Internal dosimetry of FBPA was less than that of FDG. FDG-PET study could be an acceptable screening exam for further study of FBPA-PET/CT towards BNCT.