Correlation of MIB-1 staining index and 201Tl-SPECT retention index in preoperative evaluation of malignancy of brain tumors

MIB-1 staining provides a useful index of the malignancy of brain tumors. However, because of the difficulty of evaluating malignancy based on the preoperative imaging findings, we investigated the correlation between the Tl-201-SPECT retention index (RI) and MIB-1 staining index (MIB-1 SI) to determine the usefulness of RI for preoperative evaluation of the malignancy of brain tumors. The subjects of this study were 47 patients who underwent tumor removal surgery at our hospital in 2006 and 2007. The tumors consisted of 16 intraaxial tumors (all gliomas: 9 glioblastomas, 2 anaplastic astrocytomas, 2 anaplastic oligoastrocytomas, 1 oligodendroglioma, and 2 ependymomas), 8 other malignant brain tumors, and 23 extraaxial tumors (10 meningiomas, 7 pituitary adenomas, and 6 schwannomas). The mean RI and mean MIB-1 SI of the intraaxial tumors were 0.628% and 32.0%, respectively, and after MIB-1 SI was converted to the natural logarithm (log MIB-1 SI), Pearson's coefficient for the correlation between them was significant (r = 0.752, P < 0.001). The mean RI and mean MIB-1 SI of the extraaxial tumors were 0.377% and 3.01%, respectively, and after MIB-1 SI was converted to log MIB-1 SI, Pearson's coefficient for the correlation between them was significant (r = 0.803, P < 0.001). Thus, the MIB-1 SI values of highly malignant intraaxial tumors was strongly correlated with their RI values, and the Tl-201-SPECT RI values were useful as an index of malignancy. RI values may also be useful for evaluating apparently benign extraaxial tumors for possible malignancy.