Survival after stereotactic radiosurgery of recurrent glioblastomas in patients with radical resection of primary tumor

Abstract

glioblastoma (GBM) is an aggressive tumor with high rate of recurrence and estimated survival of 15-18 months after diagnosis. Factors associated with longer survival of GBM patients are age 20 months. The survival was analyzed by Kaplan-Meier (KM) method. Log-rank test was used for analysis of the survival according to the binary predictors. The effect of several categorical factors on survival was analyzed by Pearson Chi-square test. The effect of the quantitative covariates on survival was studied by regression analysis in Cox proportional risk model. Hazard ratio was calculated with 95 % confidential intervals (CI). The analysis revealed the following. Median OS following SRS RGBM was 26.3 months (95 % CІ 17 – 45.5), median RFS was 12.9 months (95 % CІ 8.4 – 25.6), median SAR – 9.8 months (95 % CІ 6.7 – 24.4). Two-year OS in our study was 56 %. 6-month survival after SRS –77 %; one-year survival after SRS – 39 %, and two-year survival after SRS – 28 %. The significant impact of performance status (p = 0.00159), duration of recurrence-free period (p = 0.02711) and surgical resection of RGBM (р = 0.009391) on the OS was demonstrated. The best OS was shown for the patients with Karnofsky score 90, recurrence occurring after more than 20 months and previous surgical resection of RGBM. The effects of other factors on OS were not demonstrated. Such factors as age, sex, performance status, adjuvant RT with сoncomitant alkylating CHT, surgical resection of RGBM, type of recurrence, number of SRS fractions, BED11 in SRS RGBM, BED11 for overall courses of irradiation, SRS target volume demonstrated no effect on SAR. SRS is non-invasive method for RGBM treatment that allows for improving the survival without significant radiation toxicity. Primary biological properties of the tumor seem to be of priority in determining the survival of RGBM patients. Although irradiation of GBM is advantageous regarding the improvement of the survival, one could also speculate that re-irradiation of the recurrent malignant glioma triggers some changes in its biology neutralizing the potential effect of the survival factors that had predictive value before re-irradiation.

Keywords

• neoplasms, malignant glioma, glioblastoma, neurosurgical procedures, recurrence, radiosurgery, survival