title: Differential dosimetric benefit of proton beam therapy over intensity modulated radiotherapy for a variety of targets in patients with intracranial germ cell tumors.
abstract: BACKGROUND
  We performed dosimetric comparisons between proton beam therapy and intensity modulated radiotherapy (IMRT) of intracranial germ cell tumors (ICGCTs) arising in various locations of the brain.
  
  
  METHODS
  IMRT, passively scattered proton therapy (PSPT), and spot scanning proton therapy (SSPT) plans were performed for four different target volumes: the whole ventricle (WV), pineal gland (PG), suprasellar (SS), and basal ganglia (BG). Five consecutive clinical cases were selected from the patients treated between 2011 and 2014 for each target volume. Total 20 cases from the 17 patients were included in the analyses with three overlap cases which were used in plan comparison both for the whole ventricle and boost targets. The conformity index, homogeneity index, gradient index, plan quality index (PQI), and doses applied to the normal substructures of the brain were calculated for each treatment plan.
  
  
  RESULTS
  The PQI was significantly superior for PSPT and SSPT than IMRT for ICGCTs in all locations (median; WV: 2.89 and 2.37 vs 4.06, PG: 3.38 and 2.70 vs 4.39, SS: 3.92 and 2.49 vs 4.46, BG: 3.01 and 2.49 vs 4.45). PSPT and SSPT significantly reduced the mean dose, and the 10 and 15 Gy dose volumes applied to the normal brain compared with IMRT (p ≤ 0.05). PSPT and SSPT saved significantly greater volumes of the temporal lobes and hippocampi (p < 0.05) in the SS and PG targets than IMRT. For tumors arising in the BG, PSPT and SSPT also saved greater volumes of the contralateral temporal lobes.
  
  
  CONCLUSIONS
  PSPT and SSPT provide superior target volume coverage and saved more normal tissue compared with IMRT for ICGCTs in various locations. Future studies should assess whether the extent of normal tissue saved has clinical benefits in children with ICGCTs.
authors.affiliation: Center for Proton Therapy, Goyang-si, Republic of Korea. jhoon@ncc.re.kr.
authors.forename: Jeonghoon
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Soonchunhyang University Hospital, Seoul, Republic of Korea. yh810530@hanmail.net.
authors.forename: Younghee
authors.initials: Y
authors.lastname: Park
authors.affiliation: Center for Proton Therapy, Goyang-si, Republic of Korea. sung-uk.lee@ncc.re.kr.
authors.forename: Sung Uk
authors.initials: SU
authors.lastname: Lee
authors.affiliation: Center for Proton Therapy, Goyang-si, Republic of Korea. tykim@ncc.re.kr.
authors.forename: Taeyoon
authors.initials: T
authors.lastname: Kim
authors.affiliation: Center for Proton Therapy, Goyang-si, Republic of Korea. jewel@ncc.re.kr.
authors.forename: Yun-Kyung
authors.initials: YK
authors.lastname: Choi
authors.affiliation: Center for Proton Therapy, Goyang-si, Republic of Korea. jooyoungcasa@ncc.re.kr.|Center for Pediatric Cancer, National Cancer Center, Goyang-si, Republic of Korea. jooyoungcasa@ncc.re.kr.
authors.forename: Joo-Young
authors.initials: JY
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001479:Basal Ganglia; D001932:Brain Neoplasms / Q000188:drug therapy / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D003131:Combined Modality Therapy; D005260:Female; D018237:Germinoma / Q000188:drug therapy / Q000532:radiotherapy; D006801:Humans; D007223:Infant; D008297:Male; D009373:Neoplasms, Germ Cell and Embryonal / Q000188:drug therapy / Q000532:radiotherapy*; D059351:Organ Sparing Treatments; D010870:Pineal Gland; D010911:Pituitary Neoplasms / Q000188:drug therapy / Q000532:radiotherapy; D061766:Proton Therapy / Q000009:adverse effects / Q000379:methods*; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D016896:Treatment Outcome