NCOG-35. WEIGHING BENEFITS OF IMPROVED LONG TERM SURVIVAL AGAINST THE EFFECTS OF POST-RADIOTHERAPY NEUROCOGNITIVE DECLINE: ROLE OF RADIOTHERAPY FOR TREATMENT OF PEDIATRIC PRIMARY CNS NEOPLASMS

Abstract

Abstract OBJECTIVE To comprehensively review and weigh benefits of radiotherapy for pediatric primary central nervous system (CNS) tumors, which lengthens survival in the setting of potentially debilitating morbidity, including post-radiotherapy neurocognitive decline. METHODS In this review, the authors examined all the published literature analyzing results of clinical trials, case series, and technical notes on patients undergoing radiotherapy for the treatment of tumors of the central nervous system, with an emphasis on neurocognitive decline and survival outcomes. RESULTS Radiotherapy is an essential component of the treatment regimen for pediatric medulloblastoma. A recent trial demonstrated association between contemporary treatment protocols and significant post-radiotherapy neurotoxicity. A new protocol for WNT 2-driven medulloblastoma has been proposed and is undergoing testing: 18 Gy in 10 fractions plus a tumor-bed boost of 36 Gy in 20 fractions for a total primary site dose of 54 Gy in 30 fractions without concurrent chemotherapy followed by the standard six cycles of adjuvant systemic chemotherapy. Maximal surgical resection remains the mainstay of therapy for low grade glioma, as radiation therapy is reserved for subsequent recurrence or progression. Management paradigms are similar for high grade gliomas and ependymomas. Overall, radiotherapy allows for greater lifetime survival but also lengthens the morbidity from late effects, especially neurocognitive decline. This is largely due to the unintended consequence of radiation- induced damage to the normal neural tissue caught in the beam trajectory. Advancements in photon-based radiotherapy confined the volume of the brain that was irradiated to fit the tumor margins more closely; however, the advent of PBRT further allows for greater sparing of normal neuronal tissue, by maximizing energy deposition at the tumor location while minimizing energy deposition both proximal and distal to the tumor target. CONCLUSION Future research is needed to develop interventions for those already suffering from the late effects of post-radiotherapy neurocognitive decline.