CORRELATION OF TL-201 SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY AND SURVIVAL AFTER TREATMENT FAILURE IN PATIENTS WITH GLIOBLASTOMA-MULTIFORME

AFTER INITIAL RADIOTHERAPY for an intracranial malignant glioma, the m ajority of patients return at a later date with a recurrent, enhancing mass on computed tomography or magnetic resonance imaging. This mass represents either recurrent tumor, radionecrosis, or a combination of the two. The relative proportion of live versus dead tumor cells is di fficult to determine from surgical specimens of another biopsy, althou gh this has been the preferred method of assessing such ''failed'' pat ients. Recently, attention has turned to tomographic images of metabol ic markers, i.e., positron emission tomography and thallium-201 (Tl-20 1) single photon emission computed tomography, as noninvasive methods of assessing relative tumor viability. To assess whether Tl-201 uptake in vivo can be used as a prognostic indicator in patients with gliobl astoma multiforme, we measured the ratio of Tl-201 uptake in tumor to Tl-201 uptake in myocardium (T/C ratio) in 16 patients at the point of treatment ''failure'' and followed all the patients until they died. All patients died of neurological causes, and 11 of the 16 patients ha d documented viable tumor recurrence. There was a significant negative correlation between the T/C ratio at failure and the time interval be tween failure and death (r= -0.602, P = 0.014). Patients with T/C rati os of less than 0.3 lived an average of 13 months, whereas patients wi th T/C ratios of more than 0.3 lived an average of only 4 months. The value of Tl-201 single photon emission computed tomography imaging may well go beyond simply detecting radionecrosis, because three of the s ix patients with extended survival and low Tl-201 uptake had viable tu mor on a subsequent biopsy. Thus, Tl-201 single photon emission comput ed tomography imaging can be a useful noninvasive technique for catego rizing recurrent glial tumors in terms of clinical aggressiveness.