Incidence and dosimetric parameters of pediatric brainstem toxicity following proton therapy

Abstract

Background. Proton therapy offers superior low and intermediate radiation dose distribution compared with photonbased radiation for brain and skull base tumors; yet tissue within and adjacent to the target volume may receive a comparable radiation dose. We investigated the tolerance of the pediatric brainstem to proton therapy and identifi ed prognostic variables. Material and methods. All patients Ͻ 18 years old with tumors of the brain or skull base treated from 2007 to 2013 were reviewed; 313 who received Ͼ 50.4 CGE to the brainstem were included in this study. Brainstem toxicity was graded according to the NCI Common Terminology Criteria for Adverse Events v4.0. Results. The three most common histologies were ependymoma, craniopharyngioma, and low-grade glioma. Median patient age was 5.9 years (range 0.5 -17.9 years) and median prescribed dose was 54 CGE (range 48.6 -75.6 CGE). The two-year cumulative incidence of toxicity was 3.8% Ϯ 1.1%. The two-year cumulative incidence of grade 3 ϩ toxicity was 2.1% Ϯ 0.9%. Univariate analysis identifi ed age Ͻ 5 years, posterior fossa tumor location and specifi c dosimetric parameters as factors associated with an increased risk of toxicity. Conclusion. Utilization of current national brainstem dose guidelines is associated with a low risk of brainstem toxicity in pediatric patients. For young patients with posterior fossa tumors, particularly those who undergo aggressive surgery, our data suggest more conservative dosimetric guidelines should be considered.

Imaging Changes in Pediatric Intracranial Ependymoma Patients Treated With Proton Beam Radiation Therapy Compared to Intensity Modulated Radiation Therapy

“…Interaction between RT type and age was assessed. those in another recently published work (11) and will be discussed more fully in an upcoming publication.…”

“…Because the posterior fossa is a common location of ependymoma, brainstem toxicity is a major concern, and dose constraints have been published (10,11). Incomplete recovery of brainstem function after RT for infratentorial ependymoma has been related to surgical morbidity and the volume/extent of tumor (12).…”

Relating Proton Treatments to Photon Treatments via the Relative Biological Effectiveness—Should We Revise Current Clinical Practice?

“…Because planners are aware of this, beam angles are chosen carefully to avoid pointing beams directly toward a critical structure (also because of range uncertainties). In some clinical cases, pointing a beam toward the brainstem cannot be avoided, causing potential RBE values of more than 1.1 to a small area of the brainstem (8). This needs to be considered when defining constraints.…”

Myxopapillary ependymoma: a SEER analysis of epidemiology and outcomes

“…Likewise, information regarding disease progression is not present in the database. Recent advances in RT, such as proton therapy, are also not reflected in this analysis and may enhance the adoption of RT as dose to normal neural tissues is decreased [35][36][37]. The effect of chemotherapy was not analyzed for this study, though chemotherapy is not routinely used in the treatment of MPE.…”