title: Metachronous medulloblastoma and glioblastoma: Implications for clinical and technical aspects of re-irradiation.
abstract: A seven-year-old male underwent surgical resection and chemoradiation for average risk medulloblastoma; twelve years later, the presence of a necrotic and infiltrative mass in the same area and invading the brainstem prompted a subtotal resection. Pathology was indicative of glioblastoma. He was then treated with concurrent temozolomide and using biologically effective dose calculations for gross residual tumor tissue in the brainstem as well as brainstem tolerance, a radiotherapy dose of 3750 cGy was chosen, fractionated in twice-daily fractions of 125 cGy each. The gross tumor volume was expanded with a 5 mm margin to the planning target volume, which was also judiciously subtracted from the normal brainstem. He completed his radiotherapy course with subsequent imaging free of residual tumor and continued adjuvant temozolomide and remains under follow-up surveillance. This case underscores the rarity of metachronous medulloblastoma and glioblastoma, of which only five known cases heretofore have been described. We discuss the technicalities of radiotherapy planning in this patient, including common hurdles for radiation oncologists in similar patients.
authors.affiliation: Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA.
authors.forename: Vivek
authors.initials: V
authors.lastname: Verma
authors.affiliation: Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA.
authors.forename: Rajesh R
authors.initials: RR
authors.lastname: Kulkarni
authors.affiliation: Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA.
authors.forename: Abhijeet R
authors.initials: AR
authors.lastname: Bhirud
authors.affiliation: Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA.
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Bennion
authors.affiliation: Department of Pathology, University of Nebraska Medical Center, Omaha, NE, USA.
authors.forename: Rodney D
authors.initials: RD
authors.lastname: McComb
authors.affiliation: Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA.
authors.forename: Chi
authors.initials: C
authors.lastname: Lin
keywords: Brainstem tolerance; Glioblastoma; Medulloblastoma; Re-irradiation; Toxicity