Assessment of clinical usefulness of 131I alpha-methyl-tyrosine and fused SPECT/MRI imaging for diagnostics of recurrent cerebral gliomas.

BACKGROUND

Early detection and diagnostic differentiation of neoplastic tissue from necrotic changes and scars following the treatment of cerebral gliomas is essential for determining further therapy and prognosis. The primary technique used for the diagnostics of recurrent neoplastic growth is the magnetic resonance imaging (MRI), which in some cases, however, does not allow one to identify the character of cerebral lesions. Recently, MRI has been supplemented with single-photon emission computed tomography (SPECT) or positron emission tomography (PET) employing radiolabelled amino acids. e.g. tyrosine or methionine. The aim of the project was to assess the diagnostic potential of SPECT when iodine-131 alpha-methyl tyrosine (IMT), a Polish make of radiopharmaceutical (OBRI--POLATOM, Otwock-Rwierk, Poland), was applied. The use of 131I as a substitute for the more costly, imported iodine-123 has been justified in view of the nature and significance of the diagnostic problem on the one hand, and the possibility of 131-iodine application on a larger scale in CEE countries, on the other.

MATERIAL AND METHODS

MRI and SPECT were performed in 24 patients with a history of surgical treatment and radiotherapy of cerebral glioma (WHO grade II/IV). A SPECT was carried out 15 min after an i.v. injection of 74-111 MBq IMT. The tomograms were evaluated visually and in quantitative terms. The fused SPET/MR images were also analyzed. The obtained results were verified against histopathological findings, control MRI examinations and the clinical course of disease within 7-28 months of monitoring.

RESULTS

In 19 patients, an increased IMT uptake indicative of a recurrent tumour was found, and the presence of the tumour was confirmed. In five patients no hot spots were detected which would indicate the neoplastic growth and verification did not provide any evidence for relapse.

CONCLUSIONS

The examination employing iodine-131 IMT made it possible to confirm or exclude tumour recurrence in all the subjects, also in the cases when the CT/MR images were inconclusive. The MRI/SPECT fusion made it possible to more accurately identify the location of tumour recurrence as well as determine the area for spectroscopic MR analysis, for stereotactic biopsy and radiotherapy.