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[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.

MATERIALS:

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.

[Author information]

Park J1, Park Y2, Lee SU3, Kim T4, Choi YK5, Kim JY6,7.

1Center for Proton Therapy, Goyang-si, Republic of Korea. jhoon@ncc.re.kr.
2Department of Radiation Oncology, Soonchunhyang University Hospital, Seoul, Republic of Korea. yh810530@hanmail.net.
3Center for Proton Therapy, Goyang-si, Republic of Korea. sung-uk.lee@ncc.re.kr.
4Center for Proton Therapy, Goyang-si, Republic of Korea. tykim@ncc.re.kr.
5Center for Proton Therapy, Goyang-si, Republic of Korea. jewel@ncc.re.kr.
6Center for Proton Therapy, Goyang-si, Republic of Korea. jooyoungcasa@ncc.re.kr.
7Center for Pediatric Cancer, National Cancer Center, Goyang-si, Republic of Korea. jooyoungcasa@ncc.re.kr.
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