MATERIAL and METHODS: A multicenter, retrospective study (7 centers, N=236) was conducted by the Neuro-oncology Group of the Turkish Radiation Oncology Association.

RESULTS: Median overall survival (OS) was 11 months and 1- and 2-year survival rates were 48% and 22%, respectively. Survival was negatively correlated with cumulative biologically effective dose (BED10) (r=-0.158, p=0.016) and cumulative equivalent dose in 2-Gy fractions (EQD2) (r=-0.158, p=0.016). In univariate analysis, survival was associated with performance status (p<0.001), histopathology at diagnosis and recurrence (p<0.001), radiotherapy (RT) method used for recurrence (p=0.025), tumor volume at recurrence (p=0.014), cumulative EQD2 (<110 vs. ?110 Gy, p=0.038), and cumulative BED10 (<130 vs. ?130 Gy, p=0.022). In multivariate analysis, tumor volume at recurrence (HR=1.68, 95% CI=1.06-2.64, p=0.025), Karnofsky Performance Status score (HR=5.7, 95% CI=3.26-9.98, p<0.001), and histopathology at recurrence (glioblastoma vs. high-grade glioma: HR=0.48, 95% CI=0.26-0.88, p=0.019; glioblastoma vs. low-grade glial tumor: HR=0.16, 95% CI=0.08-0.34, p<0.001) were found to be independent prognostic factors. Radionecrosis was detected in 25% (n=58) of the patients. Re-resection was associated with a higher rate of radionecrosis (37.7% vs. 18%, p=0.002).

CONCLUSION: The prognostic factors most strongly associated with survival in glioma patients undergoing reirradiation were Karnofsky Performance Status score below 70, glioblastoma histopathology, and tumor volume greater than 4.5 cm3. In addition, survival time was negatively correlated with cumulative EQD2 and BED10. The rate of radionecrosis was higher in patients who underwent re-resection compared those who did not. Keywords : Malignant glioma, Reirradiation, Survival