Abstract
Background: Boron neutron capture therapy requires a 2 mM 10B concentration in the tumor. The well-known BNCT patient treatment method using boronophenylalanine (BPA) as a boron-carrying agent utilizes [18F]fluoroBPA ([18F]FBPA) as an agent to qualify for treatment. Precisely, [18F]FBPA must have at least a 3:1 tumor to background tissue ratio to qualify the patient for BNCT treatment. Normal, hyperplasia, and cancer thyroids capture iodine and several other large ions, including BF4−, through a sodium-iodine symporter (NIS) expressed on the cell surface in normal conditions. In cancer, NIS is also expressed within the thyroid cell and is not functional. Methods: To visualize the thyroids and NIS, we have used a [18F]NaBF4 positron emission tomography (PET) tracer. It was injected into the tail veins of rats. The [18F]NaBF4 PET tracer was produced from NaBF4 by the isotopic exchange of natural 19F with radioactive 18F. Rats were subject to hyperplasia and tumor-inducing treatment. The NIS in thyroids was visualized by immunofluorescence staining. The boron concentration was calculated from Standard Uptake Values (SUV) in the PET/CT images and from the production data. Results: 41 MBq, 0.64 pmol of [18F]NaBF4 PET tracer that contained 0.351 mM, 53 nmol of NaBF4 was injected into the tail vein. After 17 min, the peak activity in the thyroid reached 2.3 MBq/mL (9 SUVmax). The natB concentration in the thyroid with hyperplasia reached 381 nM. Conclusions: Such an incorporation would require an additional 110 mg/kg dose of [10B]NaBF4 to reach the necessary 2 mM 10B concentration in the tumor. For future BNCT treatments of thyroid cancer, contrary to the 131I used now, there is no post-treatment radioactive decay, the patient can be immediately discharged from hospital, and there is no six-month moratorium for pregnancy. This method can be used for BNCT treatment compounds of the type R-BFn, where 1 <= n <= 3, labeled with 18F relatively easily, as in our example. A patient may undergo injection of a mixture of nonradioactive R-BFn to reach the necessary 10B concentration for BNCT treatment in the tumor together, with [18F]R-BFn for boron mapping.
Highlights
Radiation treatment is one of the widely accepted and used forms of cancer treatment
The boron concentration was calculated from Standard Uptake Values (SUV) in the positron emission tomography (PET)/CT images and from the production data
For future boron neutron capture therapy (BNCT) treatments of thyroid cancer, contrary to the 131 I used there is no post-treatment radioactive decay, the patient can be immediately discharged from hospital, and there is no six-month moratorium for pregnancy
Summary
Radiation treatment is one of the widely accepted and used forms of cancer treatment. Cells 2020, 9, 2084 these types of irradiation is that the beam energy is deposited on the track before reaching the tumor. In boron neutron capture therapy (BNCT), this effect is further reduced, as the target is defined by the presence of 10 B in the injected drug and its distribution. Boron neutron capture therapy requires a 2 mM 10 B concentration in the tumor. The well-known BNCT patient treatment method using boronophenylalanine (BPA) as a boron-carrying agent utilizes [18 F]fluoroBPA ([18F ]FBPA) as an agent to qualify for treatment. Hyperplasia, and cancer thyroids capture iodine and several other large ions, including BF4 − , through a sodium-iodine symporter (NIS) expressed on the cell surface in normal conditions. NIS is expressed within the thyroid cell and is not functional. Methods: To visualize the thyroids and NIS, we have used a [18 F]NaBF4 positron emission tomography (PET)
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