Use of proton therapy for re-irradiation in pediatric intracranial ependymoma.

Abstract

To report disease control, survival and treatment-associated toxicity with the use of proton therapy (PRT) for re-irradiation of intracranial ependymoma. Twenty patients underwent 33 PRT re-irradiation courses for recurrent or metastatic lesions between June 2004 and February 2015 at Massachusetts General Hospital. The majority of patients were female (60%), with infratentorial tumors (90%), anaplastic histology (55%), and initially received 55.8 GyRBE (52.2-59.4) involved field (IF) PRT. First failure was local (55%), distant (30%) or both (15%) at a median time of 23.9 months (9.9-98.5) from first treatment. Salvage therapy included re-resection (75%), chemotherapy (60%) and IFPRT (70%) to a median dose 50.4 GyRBE (35-55.8) in the majority of patients. The median follow-up was 37.8 months (5.5-138.0). Three year OS and PFS are 78.6% (95% CI 67.6-89.6) and 28.1% (95% CI 15.6-40.6), respectively. Longer OS was significantly associated with surgical resection of recurrent disease (HR 9.19, 95% CI 1.27-66.44, p=0.028). The pattern of second failure after re-irradiation was directly related to the pattern of first failure (p<0.01). Three of 14 patients (21.4%) locally re-treated experienced grade 2 radiation-associated treatment change. Proton therapy appears safe and efficacious for the re-treatment of recurrent intracranial ependymoma.