title: Analysis of dose at the site of second tumor formation after radiotherapy to the central nervous system.
abstract: OBJECTIVE
  Second tumors are an uncommon complication of multimodality treatment of childhood cancer. The present analysis attempted to correlate the dose received as a component of primary treatment and the site of the eventual development of a second tumor.
  
  
  METHODS
  We retrospectively identified 16 patients who had received radiotherapy to sites in the craniospinal axis and subsequently developed a second tumor. We compared the historical fields and port films of the primary treatment with the modern imaging of the second tumor locations. We classified the location of the second tumors as follows: in the boost field; marginal to the boost field, but in a whole-brain field; in a whole-brain field; marginal to the whole brain/primary treatment field; and distant to the field. We divided the dose received into 3 broad categories: high dose (>45 Gy), moderate dose (20-36 Gy), and low dose (<20 Gy).
  
  
  RESULTS
  The most common location of the second tumor was in the whole brain field (57%) and in the moderate-dose range (81%).
  
  
  CONCLUSIONS
  Our data contradict previous publications that suggested that most second tumors develop in tissues that receive a low radiation dose. Almost all the second tumors in our series occurred in tissue within a target volume in the cranium that had received a moderate dose (20-36 Gy). These findings suggest that a major decrease in the brain volume that receives a moderate radiation dose is the only way to substantially decrease the second tumor rate after central nervous system radiotherapy.
authors.affiliation: Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Galloway
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Indelicato
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Amdur
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Morris
authors.forename: Erika L
authors.initials: EL
authors.lastname: Swanson
authors.forename: Robert B
authors.initials: RB
authors.lastname: Marcus
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000209:etiology / Q000532:radiotherapy*; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging / Q000209:etiology; D002490:Central Nervous System / Q000528:radiation effects*; D002648:Child; D002675:Child, Preschool; D016371:Cranial Irradiation; D005260:Female; D005500:Follow-Up Studies; D005910:Glioma / Q000000981:diagnostic imaging / Q000209:etiology; D006801:Humans; D007223:Infant; D008297:Male; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging / Q000209:etiology; D008579:Meningioma / Q000000981:diagnostic imaging / Q000209:etiology; D009381:Neoplasms, Radiation-Induced / Q000000981:diagnostic imaging / Q000209:etiology*; D016609:Neoplasms, Second Primary / Q000000981:diagnostic imaging / Q000209:etiology*; D011859:Radiography; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D012509:Sarcoma / Q000000981:diagnostic imaging / Q000209:etiology; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000209:etiology; D013997:Time Factors