Clinical significance of thallium-201 SPECT after postoperative radiotherapy in patients with glioblastoma multiforme.

To assess the clinical significance of 201Tl-SPECT after postoperative radiotherapy in patients with glioblastoma multiforme (GM). Eighteen patients with macroscopically residual GM who underwent 201Tl-SPECT just after postoperative radiotherapy were analyzed. Fifteen patients (83%) received radiotherapy with a total dose of 60 Gy in conventional fractionation, and the remaining three patients were treated with 72 Gy with hyperfractionation schedules. Sixteen patients (89%) were treated with chemotherapy that consisted of procarbazine, nimustine (ACNU) and vincristine. Concerning 201Tl-SPECT, we calculated the radioactivity ratio of the tumors to contralateral normal brain (T/N ratio) on early and delayed images after 111 MBq 201Tl chloride injections. The median follow-up of all 18 patients was 14.7 months (range, 2.7-38.0 months). At the time of this analysis, 15 patients (83%) had died, and the 1-year overall survival and the median survival time were 67% and 16.2 months, respectively. Fifteen patients (83%) had disease recurrence, and the 1-year progression-free survival (PFS) rate and the median time to progression in all 18 patients were 29% and 7.6 months, respectively. Patients with a high early T/N ratio had a significantly poorer PFS than those with a low T/N ratio (P = 0.0131). On univariate analysis, early T/N ratio alone had a significant impact on PFS, and on mutivariate analysis, early T/N ratio alone was a significant prognostic factor for PFS. 201Tl-SPECT after postoperative radiotherapy was predictive of PFS in patients with macroscopically residual GM.