Clinical observation of 32P metabolic mode at the level of sub-target nuclides

The aim of this paper was to observe the metabolic mode of 32P at the level of sub-target nuclides.

Twenty-one cancer patients were locally injected with 32P-labelled glass microspheres and then observed to determine the equalization of 32P radionuclide metabolism in the tumor target. We imaged 3 sub-target regions of interest (ROI) 1/3 the size in both the anterior and posterior directions by bremsstrahlung single-photon emission computed tomography (SPECT) X-ray imaging. The radiation dose parameters of the beta rays including the initial dose rate, the effective half-life, and the effective half-life of the cumulative radiation dose were then calculated.

The radionuclide metabolism of the 21 complete tumor targets complied with the mono-compartmental model of index metabolism, but the level of tumor control did not correlate with radiation dose parameters. In contrast, the radionuclide metabolism of the 63 sub-targets did not comply with the mono-compartmental model. Instead, 32 sub-targets were better represented by bi-compartmental or tri-compartmental metabolic models. None of the remaining 31 sub-targets complied with index metabolism.

The complexity of the radiation dose at the sub-target level partially explains poor local tumor control. Future studies will be required to improve the expression of internal exposure to radiation dose parameters.