Correlation Between SPECT/CT and IDH Mutation in Brain Glioma

Every year, nearly100,000 people worldwide are diagnosed as having brain gliomas. Although it comprises <1% of all newly diagnosed cancers, brain glioma is associated with substantial mortality and morbidity. Gliomas are intrinsic brain tumors that originate from neuroglial progenitor cells. Conventional therapies, including surgery, chemotherapy, and radiotherapy, have achieved limited improvements in the prognosis of glioma patients.

Radiation therapy to the brain may lead to postradiation injury which typically occurs within the first 3 to 12 months after radiotherapy but it was reported up to several years and even decades later. The clinical picture of radiation necrosis (RN) is variable and may include seizures, headache, personality changes, and neurologic deficits. These symptoms mimic tumor recurrence and differentiation between the two entities clinically or even by conventional radiological modalities is difficult but is necessary because the two conditions have different treatment modalities and prognosis.

SPECT has the advantages of being widely available and not expensive. Multiple SPECT tracers have been explored. Of them Thallium-201 and 99 mTc-MIBI are, possibly, the most extensively discussed. The main disadvantage of 201Tl is the lower spatial resolution, relatively large radiation dose, and the reported high false positive results. Normal uptake of MIBI in the choroid plexus may be confounding for assessing tumors around the ventricles.

Pentavalent 99mTc dimercaptosuccinic acid (99mTc (V) DMSA), is a nonspecific tumor targeting SPECT radiotracer, that has been used for imaging of various tumors including lung and breast carcinoma. However, to date, scarce reports discussed the utility of DMSA-V in patients with glioma.

Isocitrate dehydrogenase (IDH) enzymes, of which there are three isoforms, are essential enzymes that participate in several major metabolic processes, such as the Krebs cycle, glutamine metabolism, lipogenesis and redox regulation.

Major advances in cancer genetics over the past decade have revealed that the genes encoding IDHs are frequently mutated in a variety of human malignancies, including gliomas, acute myeloid leukaemia, cholangiocarcinoma, chondrosarcoma and thyroid carcinoma.