J Korean Neurosurg Soc.  2018 May;61(3):386-392. 10.3340/jkns.2018.0004.

Radiation Therapy against Pediatric Malignant Central Nervous System Tumors : Embryonal Tumors and Proton Beam Therapy

• Lim DH

• KMID: 2417363
• DOI: http://doi.org/10.3340/jkns.2018.0004

Abstract

Radiation therapy is highly effective for the management of pediatric malignant central nervous system (CNS) tumors including embryonal tumors. With the increment of long-term survivors from malignant CNS tumors, the radiation-related toxicities have become a major concern and we need to improve the treatment strategies to reduce the late complications without compromising the treatment outcomes. One of such strategies is to reduce the radiation dose to craniospinal axis or radiation volume and to avoid or defer radiation therapy until after the age of three. Another strategy is using particle beam therapy such as proton beams instead of photon beams. Proton beams have distinct physiologic advantages over photon beams and greater precision in radiation delivery to the tumor while preserving the surrounding healthy tissues. In this review, I provide the treatment principles of pediatric CNS embryonal tumors and the strategic improvements of radiation therapy to reduce treatment-related late toxicities, and finally introduce the increasing availability of proton beam therapy for pediatric CNS embryonal tumors compared with photon beam therapy.

Keyword

Child; Neoplasm; Brain; Radiation therapy; Proton beam therapy

MeSH Terms

Brain
Central Nervous System Neoplasms*
Central Nervous System*
Child
Humans
Proton Therapy
Protons
Survivors
Protons

Figure

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  Fig. 1. COG ACNS 0331 study diagram for standard-risk medulloblastoma. For children aged 3 to 7 years, CSI dose (23.5 Gy vs. 18.0 Gy) and boost radiation volume (primary site only versus entire posterior fossa) are randomized (A). For children aged 8 years or more, only boost radiation volume is randomized (B). COG : Children's Oncology Group, CSI : craniospinal irradiation, PF : posterior fossa, VCR : vincristine, CDDP : cisplatin, CCNU : lomustine, CPM : cyclophosphamide.

• 

  Fig. 2. Relative dose of proton and photon beams according to depth. The majority of proton’s energy is released within a few millimeters of Bragg peak (black arrow).

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  Fig. 3. Sagittal (A) and axial (B) computed tomography images showing radiation dose distributions. Red lines show the planning target volume and red color areas are regions irradiated with 100% of prescribed doses. Proton beam has no exit dose beyond Bragg peak and yellow arrows show that there is little radiation to normal organs such as heart, liver and bowels which are located at the front of the radiation target (red lines) in proton beam therapy. It can decrease the risk of second malignancies from radiation.

Reference

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