DETECTION OF RECURRENT GLIOMAS WITH QUANTITATIVE TL-201 TC-99M HMPAO SINGLE-PHOTON EMISSION COMPUTERIZED-TOMOGRAPHY

Deteriorating clinical status after high-dose radiation therapy for high-grade gliomas may be due to radiation changes or may signal recurrent or residual tumor mass. The two conditions cannot be distinguished reliably by computerized tomography (CT) or magnetic resonance (MR) imaging. The authors assessed the ability of sequential thallium-201 chloride (Tl-210) and technetium-99m hexamethylpropylene amine oxime (Tc-99m HMPAO) single-photon emission CT (SPECT) to distinguish tumor recurrence from radiation changes after high-dose (greater-than-or-equal-to 600 cGy) radiation therapy for malignant gliomas. Preoperative tumor/nontumor uptake ratios were analyzed in 32 patients and correlated with the presence of gross tumor at the time of reoperation. In 12 of 13 patients with Tl-201 tumor/scalp ratios of 3.5 or greater, recurrent tumor was present. The authors found Tc-99m HMPAO SPECT to be useful for identifying the absence of solid tumor recurrence in patients with low to moderate Tl-201 uptake (ratio 1.1 to 3.4) and low perfusion to that site. In 11 of 12 patients with Tc-99m HMPAO tumor/cerebellum ratios of 0.50 or less, no recurrent tumor mass was present. Three of seven patients with Tl-201 ratios of 3.4 or less and Tc-99m HMPAO ratios of 0.51 or more had recurrent tumor found at surgery; thus the test.was not predictive in this group. It is concluded that the use of sequential Tl-201 and Tc-99m HMPAO SPECT accurately identifies the presence of tumor recurrence versus radiation changes in most patients with high-grade astrocytomas who have undergone tumor resection and high-dose radiation therapy.