It is well known that radiotherapy to brain metastases might cause neurocognitive dysfunction in a substantial proportion of the patients. We investigated the clinical availability of stereotactic statistical analysis of brain perfusion SPECT using 3-dimensional stereotactic surface projections (3D-SSP) to estimate the influence of radiotherapy on brain function.
The subjects were 12 patients harboring brain metastases. Age: 52-83. Performance status: 0-3. The primary sites were lung (10) and breast (2). Whole brain, partial brain, and stereotactic radiotherapy (WBRT, PBRT and SRT) were delivered to 9, 1 and 2, respectively. As to previous treatment, 2 were irradiated more than 1 year ago, one by stereotactic radiosurgery and the other by prophylactic WBRT. Before and 2-4 months after radiotherapy, if possible, MRI, brain perfusion SPECT/ 3D-SSP and mini-mental state examination (MMSE) were performed.
1) Regional cerebral blood flow (rCBF) decreased in the areas including tumor and perifocal edema, though often undetectable for small tumors. 2) Previous treatment did not lead to apparently decreased rCBF. 3) The MMSE scores before treatment were 25/30 or more for 10, except for 2, one with 19/30 and the other who rejected the examination. 4) For 6, analyses by 3D-SSP and MMSE were serially performed. Two of the 4 who received WBRT showed decreased rCBF, diffusely distributed, as well as decreased MMSE score (<24/30). The remnant 2 showed no changes for both. On the other hand, one who received PBRT showed decreased rCBF, consistent with the beam lay-out, but the MMSE score was maintained more than 25/30. The other who received SRT showed no change in rCBF, but the MMSE score decreased from 26 to 21/30. In this case, a part of radiation beams passed through bilateral hippocampi.
Radiotherapy appeared to have a risk to decrease rCBF, which could be detected by 3D-SSP analysis. However, the influence on brain/ neurocognitive function was clinically varied and complicated.
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All authors have declared no conflicts of interest.