The Feasibility Of Re-Irradiation Using Intensity-Modulated Radiation In Selected Patients With Recurrent Gliomas

The aim of this study is to determine the feasibility and early results following IMRT re-irradiation in patients with recurrent gliomas. The secondary aim is the estimation of toxicity in relation to cumulative radiation dose. Between 2010 and 2018, 54 adult patients with recurrent gliomas have been re-irradiated with IMRT at the time of tumor recurrence or progression. There were 24 women and 30 men with mean age 38,5y (range 18-70 y). The primary histological diagnosis included: low grade gliomas in 32 pts and high grade gliomas in 22 pts. Tumor recurrence was confirmed in gadolinium MRI in all patients. 28 pts were re-operated or re-biopsied and the microscopic diagnosis was established: 22 patients with HGG and 6 patients with LGG. The median time between primary radiotherapy and re-irradiation for the whole group was 72.5 mos (range, 10.3-178.6 mos). Primary radiotherapy was performed with 3DCRT in 27 pts and IMRT in 26 pts with mean dose was 57Gy (range, 50-60 Gy). Secondary irradiation was delivered using IMRT technique with mean doses of 38.5 Gy (range, 16-54 Gy). Stereotactic boost to recurrent tumor was used (mean dose 12.7 Gy, range 6-20 Gy) in 14 patients. Chemotherapy was administered in group of 31 patients either with concurrent temozolomide or sequential PCV. For all available cases, the sum of doses from all radiotherapy courses was calculated with a platform enabling the deformable fusion of CT images and dose distribution from first and sequential radiotherapy. As a result, a total dose distribution could be obtained on the latest CT image set. The summary plan was evaluated on the basis of dose-volume histogram, calculated for critical structures and irradiated volumes. The mean cumulative tumor dose was 95.9 Gy (62-114 Gy/g). Median follow-up time from primary diagnosis was 107 mo (range, 22-358 mos) and 22 mos (range, 0.8-108 mos) from reirradiation. Median time to recurrence for LGG and HGG was 81 mos and 42 mos, respectively. All but two patients completed the planned course of radiotherapy. The irradiation was well tolerated. In four cases radiological signs of radio necrosis were observed. The response was assessed in MRI three months after completion of radiotherapy: 19 pts. achieved complete or partial response, stable disease was observed in 27 pts. Two patients progressed. Radio necrosis was diagnosed in five pts in course of observation. Median survival after re-irradiation was 23.5 mos (0.8-113 mos). Median TTP was 19.6 mos (range, 0.3-72 mos). There were no difference in PFS and OS according to PS at re-irradiation, gender, age, and primary histology. Reirradiation is one of the treatment options for recurrent gliomas and IMRT can be a feasible treatment modality without increased toxicity and it may provide a clinical benefit. Cumulative brain doses in the range of 100 Gy did not result in substantial number of radiation necrosis.