Third Course of Radical Intent Conformal Radiation in Patients with Primary Brain Tumors

Reirradiation is increasingly considered in patients with recurrent primary brain tumours. However, second course of radical reirradiation (RT2) or third course of radiation (RT3) delivering higher doses is uncommon. The current study was undertaken to report the clinical outcomes after the third course of radical radiation.

The patients undergoing three courses of cranial radiation were obtained from the radiation oncology database. The clinical and treatment details were obtained by reviewing electronic medical records and radiation charts and plans when available. Treatment outcomes, including disease status and radionecrosis, were assessed by reviewing imaging. Analysis was done using descriptive statistics and survival outcomes using Kaplan-Meier survival plots.

Eight patients were identified between 2015 and 2023 treated with a third course of radiotherapy (second reirradiation). Histopathology included ependymoma in seven and glioblastoma in one patient. The median age during first radiation was 13.5 years (range: 4-31 years) with interquartile range (IQR) of 7-26 years, and during RT3 was 22 years (range: 9-43 years, IQR: 14-32 years). The median doses at RT1, RT2, and RT3 were 59.4 Gy (IQR: 54.80-60 Gy), 54 Gy (IQR: 51.3-54.0 Gy), and 50.4 Gy (IQR: 50.0-50.4 Gy), respectively. The median interval between RT1 and RT2 was 37 months (IQR: 29-63 months), RT2 and RT3 was 39 months (IQR: 25-67 months). The median cumulative EQD2 from three courses was 153Gy₂ (IQR: 148.7-159.1 Gy₂). After 3rd course, the median follow-up was 25 months (IQR: 15-37 months) with a 2-year overall survival of 85%. One patient had developed symptomatic radionecrosis 14 months after RT3 and was treated with bevacizumab.

The third course of radical dose of radiation can be considered a reasonable approach for tumours with local recurrence after a reasonable interval of at least two years between each course, allowing for tissue recovery.