Tumour surface area as a prognostic factor in primary and recurrent glioblastoma irradiated with Ir implantation

Abstract

Background

To evaluate the impact of tumour surface area (TSA) on survival of patients treated with ¹⁹²Ir implantation for glioblastoma multiforme (GBM).

Methods/Materials

The analysis of survival and prognostic factors was performed based on a retrospective study group of 120 patients (74 males and 46 females; mean age 53 years; mean KPS score 74.6) irradiated with ¹⁹²Ir for GBM between 1999 and 2003. There were 72 (60%) patients with recurrent and 48 (40%) with primary inoperable tumour. Patients with recurrences were initially treated with surgery and external beam radiotherapy (EBRT; mean total dose (MTD) 53.5Gy). Individuals with primary inoperable glioblastoma underwent EBRT (MTD 37.2Gy) after brachytherapy completion. All patients were irradiated with ¹⁹²Ir with a total dose of 15Gy given in 5 fractions.

Results

For the total group of patients 1-year and 2-year survival were 22% and 11%, respectively, with a median survival time (MST) of 6.1 months. The multivariate Cox analysis of the best fit (Chi²=22.98, p=0.000041) distinguished such variables as: patient age (p=0.002), performance status (p=0.04) and tumour surface area (p=0.04) to significantly affect survival. Patients with TSA<90 cm² had better prognosis compared to those with TSA≥90cm² (p<0.001).

Conclusions

Tumour surface area is an independent prognostic factor in patients irradiated with ¹⁹²Ir for glioblastoma multiforme. TSA less than 90cm² predicts significantly longer survival and appears to be a more powerful prognostic variable than tumour volume.