FBPA PET/CT: to distinguish radiation necrosis from recurrent brain tumor

Objectives: It is still challenging to distinguish tumor recurrence from post radiation cerebral necrosis by magnetic resonance imaging (MRI) alone or with fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) and other available PET tracers. L-4-borono-2- ¹⁸F-fluoro-phenylalanine (¹⁸F-FBPA) is an L-type amino acid transporter (LAT1) which is specifically expressed in cancer cells membrane. In this study, we aimed to validate ¹⁸F-FBPA PET/CT as a useful modality to differentiate between these two entities.

Methods: 12 patients of glioblastoma (9), malignant meningioma(1), hemangiopericytoma(1), and metastatic brain tumors(1) who had been previously treated with radiotherapy were studied by means of FBPA PET/CT scan. A diagnosis of recurrent tumor or radiation necrosis was made on the basis of clinical course and MRI. After four hours fasting, ¹⁸F-FBPA (3.7MBq/kg) was administered intravenously for each patient. Whole-body PET/CT scan, using Eminence SOPHIA SET-3000 BCT/X (Shimadzu, Kyoto, Japan), was performed 60 minutes after ¹⁸F-FBPA administration. Scan data were analyzed using PMOD image analysis software (PMOD Technologies). Spherical volumes of interests (VOI) were set by encompassing the lesion with reference to an MRI. Maximum standardized uptake values (SUVmax) were measured.

Results: SUVmax of FBPA PET/CT scan were significantly higher for tumor recurrence than for radiation necrosis. The mean SUVmax in tumor recurrence was 4.6 ±1.2 SD, while in radiation necrosis it was 1.9 ±0.4 SD (P =0.0028).

Conclusion: ¹⁸F-FBPA PET/CT can constitute a potential method to differentiate tumor recurrence from radiation necrosis in patients with primary or metastatic brain tumors who have received radiation therapy. LAT1 specific PET biomarker ¹⁸F-FBPA can be exclusively used to detect cancer cells. Research Support: