QOS-47: EARLY DEVELOPMENT OF LOW-GRADE BONE NEOPLASM AFTER RADIATION THERAPY IN BRAIN TUMOR PATIENTS

Development of bone neoplasms secondary to radiation is well documented, with an average latency of onset for 8 years or more. We present two cases of development of early onset low-grade bone neoplasms after receiving craniospinal irradiation (CSI) as a component of the treatment for their high-grade neoplasms. Patient 1 underwent gross total surgical resection of classic medulloblastoma with spinal drop metastases. Post-resection therapy following COG protocol ACNS0332, Regimen D was instituted. The patient received proton therapy with 55.8Gy along with concurrent carboplatin and vincristine. Forty-three months post radiation; surveillance scans noted a lytic lesion in the left fronto-parietal calvarium. Surgical resection was performed revealing an atypical fibroblastic neoplasm. Patient 2 underwent gross total surgical resection of a left frontal lobe primitive neuroectodermal tumor (PNET). This was followed by treatment according to ACNS0332 Regimen A, with 55.8Gy photon radiation with concurrent vincristine. Seventeen months post irradiation, surveillance scan revealed a left occipital lytic skull lesion. Surgical resection was performed. Pathological analysis was consistent with a benign fibro-osseous lesion, however cytogenetic analysis found three different neoplastic clones. Three months later, another lesion (right parietal) developed with the same characteristics. Both patients have been followed with serial observation imaging and have had no further recurrence of these bony lesions and no progression of their primary disease. The early onset of these lesions is unusual and concerning for possible increased risk of recurrence or development of future complications such as second malignancy.