小児脳幹グリオーマに対する放射線治療の評価—CT所見と治療に対する反応

Evaluation of Radiation Therapy for Pediatric Brain Stem Glioma by Computed Tomography:CT findings and tumor response to radiotherapy

I．はじめに

　小児脳幹グリオーマ（brainstem glioma）に対する治療は，その発生部位の特殊性のため外科的治療には制約があり，放射線療法を主体として補助的に化学療法や減圧術なども併用されている^{3,4,8,12,15,19）}．

　Brain stem ghomaに対して放射線治療を行うと多くの症例でCT上臨床上の寛解がみられ生存期間も延長すると報告されている^{7,9,15,17,20）}．しかしながらその効果は一時的であって腫瘍の再増大を来たし平均生存期間は1年未満であることなどから否定的な意見もみられ^10,11），本腫瘍に対する放射線治療については必ずしも一定の評価は得られていない．

Abstract

The effects of radiation therapy on 29 brain stem gliomas in childhood were evaluated by computed to-mography (CT). The patients received radiation of 2 Gy/day as a single fraction, 5 day a week with a total dose of 40 to 60 Gy. Initial CT findings of brain stem gliomas were divided into two types : diffuse and loca-lized. Of 29 children, 5 had localized and 24 had diffuse tumor. Histological diagnoses were available for 18 pa-tients, 4 with localized and 14 with diffuse tumor. All of the localized tumors were astrocytomas and diffuse tumors included 13 anaplastic gliomas (glioblastomas), 3 anaplastic astrocytomas, and one astrocytoma. Complete response or partial response to radiation therapy was observed on CT in 100% (5/5) of the localized tumors and 46% (11/13) of the diffuse tumors at the first evaluation.

Contrary to expectation, low-grade gliomas re-sponded much better to radiation therapy than high-grade gliomas. The response rates were 80% (4/5) in astrocytoma, 67% (2/3) in anaplastic astrocytoma, and 38% (5/13) in anaplastic glioma.

In the follow-up CT after radiation therapy, a de-layed effect was observed in only one of the 24 diffusetumors. Nine of 10 children who had a re-irradiation following the recurrence experienced very little benefit.

None of the patients with localized tumors have shown evidence of tumor progression or recurrence, and the quality of their life has been excellent. On the other hand, all of the patients with diffuse tumor died within 20 months after initial treatment.

The results of this study suggest that radiation ther-apy is beneficial for localized tumors but not for diffuse tumors, and new treatments need to be developed for diffuse tumors.