A Prospective Study of Conventionally Fractionated Dose Constraints for Reirradiation of Primary Brain Tumors in Children

Abstract

Objective

Reirradiation is increasingly considered for recurrent pediatric brain tumors, but dosimetric guidelines are lacking. To identify composite dose-volume constraints for reirradiation of recurrent brain tumors in children, a prospective trial was conducted.

Methods

Nine children with recurrent brain tumors previously treated with radiation were prospectively reirradiated. Three had GBM, two had AT/RT, and one each had ependymoma, NGGCT, medulloblastoma, or meningioma. For all patients, DICOM format records of their prior radiation (RT1) fields were obtained and deformed onto the CT simulation for their second course of radiation (RT2). Conventionally fractionated treatment plans for RT2 satisfied dose constraints for RT2 alone and the composite sum of both courses (RT1+RT2). The primary endpoint was the rate of symptomatic brain necrosis at 6 months after RT2.

Results

Median age at RT2 was 9.7y (range, 2.9 -6.8 y). Median interval between RT1 and RT2 was 19 months (range, 7–82 months). Treatment modality for RT2 was VMAT for seven patients and proton therapy for two patients. Median prescription dose for RT2 was 45 Gy (range, 30.6-60 Gy). Five patients were evaluable for the primary endpoint; none had symptomatic brain necrosis at 6 months after RT2. Four patients were not evaluble at 6 months due to death (n=2) or transition to hospice (n=2) by 6 months, all due to progression of disease. Median overall survival from RT2 start for all patients was 10.7 months (range, 5.2-46.4 months).

Conclusions

This prospective study suggests that conventionally fractionated reirradiation for recurrent brain tumors in children may be performed safely. These results provide a starting point for development of dose-volume constraints for pediatric brain reirradiation. Advanced technologies such as proton therapy may allow for reirradiation dose escalation while minimizing dose to surrounding critical structures.