あった. 2月 6日右後頭葉病変に対し, 開頭生検術を施 行.2月 26日 MRI 上他病変の増大あり.病理診断にてト キソプラズマの診断にて, HIV抗体を検査したところ陽 性であった. CT, MRI 及び病理組織を供覧します. 当科 では, HIV抗体はルーチーンで行っておらず, 先ずは鑑 別 診 断 に 挙 げ る こ と が 肝 要 と 思 わ れ る. 治 療 は, pyrimethamineと sulfadiazineの併用経口投与が有効で した.
一般演題・第２部>
座長：斉藤 太（佐久 合病院 脳神経外科） ５．日高病院における転移性脳腫瘍に対するガンマナイ フ治療 柴崎 徹，坐間 朗，大江 千廣 （日高病院 脳神経外科） 【目 的】 転 移 性 脳 腫 瘍 に お け る ガ ン マ ナ イ フ 治 療 (LGK) の役割・意義・問題点について検討する. 【対 象】 日高病院ガンマナイフセンター (当院) で 1991年 5月 よ り 2003年 12月 ま で に LGK を 施 行 し た 脳 転 移 637例 (年齢 : 15歳-88歳,男 395例 女 242例)を対象と した. 原発巣の内訳は肺癌 50％, 大腸癌 13％, 乳癌 11％, 腎 細 胞 癌 7％, 原 発 巣 不 明 4％, そ の 他 15％で あった. 【方 法】 LGK の標準的方法で行い腫瘍「辺縁」線量 10 -32Gy, 中心線量 21-55Gyを用いた. 多発性転移例 (10 病巣以上) では複数回 (日) に けて行ったが, 原則一回 の照射とした. 【結 果】 当院の LGK 全症例数に占 める脳転移の割合は全世界症例統計 (32.5％) と同等で あったが, 国内統計 (53.5％) よりは低かった. 局所制御 (CR, PR, NC) は約 90％で, ほとんどの例で神経死が回 避できた. 【 察】 LGK は脳転移治療において放射 線療法の目的・意義である「脳神経症状や頭蓋内圧亢進 症状を改善し, 患者の生活レベルを維持ないし改善する. 脳転移そのものが死因とならないようにする.」に合致し た方法として有効であるが, 誤」診例や適応拡大の問題 点も指摘されなければならない. 【結 論】 LGK が治 療法として確立するためにはそれ自体の手技・手法の なる発展やランダム化比較試験が必要と思われる.６．Gamma Knife Radiosurgery for Patients with Brain Metastases : A Paradigm Change from WBRT to the Present Era
Masaaki Yamamoto, MD
（Katsuta Hospital Mito Gamma House） Most fortunately,we already live in a new era when a tumor with a volume of 0.005 cc or even slightly smaller
can be detected with thin slice, post-enhanced MR images. Also, a single metastatic lesion can now be irradiated with a sharply focused irradiation technique. We no longer need to indiscreetly irradiate the innocent normal brain as was formerly done with WBRT,possibly leaving the patient at risk for future dementia. Based on my personal series of more than 1000 patients(more than 1400 procedures) who underwent GK radiosurgery for brain METs during a 10 year period, I will discuss the paradigm change from the former treatment standard, WBRT, to the present era. I will also stress the numer-ous advantages of GK treatment,,an option preferable to WBRT, for patients with multiple lesions What is the minimum size of lesions detectable on MR images? If we use a recently-developed 1.5 Tesla MR unit,the minimal lesion volume detectable with a routine examination using a 5 mm slice thickness and a single dose of gadolinium, is 0.5004 cc. Such a small metastatic lesion cannot be found in a routine macroscopic autopsy study. Instead of worrying about invisible brain METs and performing WBRT, therefore, meticulous MR imaging examinations must be repeated at intervals of no more than three months. If new lesions appear,GK radiosur-gery should be repeated. How many lesions can be treated with a GK? Theoretically, there is no tumor number limitation in GK radiosurgery. However, as a practical matter in daily practice, 30-40 lesions are the upper limit that can be treated in a one-day session because of the prolonged procedure time. If a patient has more than 40 lesions,the procedure should be divided into two sessions of one day each.
What are the merits of GK radiosurgery for multiple METs? In my personal experience,the number of tumors treated with GK radiosurgery markedly influences the survival period. However, approximately 80％ of patients with brain METs did not die due to brain disease progression regardless of tumor number. Is GK radiosurgery more advantageous than WBRT? Yes, absolutely,and for several reasons: Only a brief hospital stay is necessary. We achieve higher control rates and earlier symptom palliation. All observable lesions on MRI can be treated even if the lesions are radioresistant. Other treatments,such as radiation therapy for other parts of the body,surgery and chemotherapy,do not have to be interrupted. Procedures can be repeated, even after WBRT. Hair loss is far less severe than with WBRT, with most patients retaining some hair. A negligible 第 33回群馬脳腫瘍研究会
incidence of dementia can reasonably be expected. Is GK treatment for multiple METs safe? A Rand phan-tom experiment based on a real treatment protocol, in which 48 lesions were treated in one patient, yielded estimated cumulative irradiation doses to the normal brain of 8.85-13.4 Gy in areas close to the lesions and 2.60-3.55 Gy in areas at some distance from the lesions. Also,I calculated the cumulative irradiation doses to the normal brain using the treatment protocols of more than 100 patients who underwent GK radiosurgery for 10 or more METs. The integral doses to the whole normal brain were estimated to be 4.0-6.0 Joules in most patients. These estimates show that cumulative irradiation doses for patients with numerous radiosurgical targets apparent-ly do not exceed the threshold level for normal brain necrosis.
Does diffuse white matter change often seen after WBRT also occur after GK for multiple brain METs? It is well known that considerable numbers of patients who had WBRT experienced mental state deterioration. In such patients, both autopsy and MR images showed diffuse white matter changes (DWMC). My recent ana-lyses are based on 45 patients referred to us who had
undergone WBRT. MR images obtained 6-42 (mean ; 16) months after WBRT demonstrated DWMC in 21 (47％) of these 45 patients. DWMC occurred in 8％, 50％, 63％ and 84％ of the patients, respectively, 6,12,18 and 24 months after WBRT. In contrast, I recently analyzed 60 patients who underwent GK radiosurgery alone for 5 lesions or more. Follow-up MR images were obtained more than 6 months after treatment in all 60. Images obtained 7-56 (mean ; 14) months after treatment demonstrated no DWMC in any of the 60 patients.
In conclusion,WBRT should be postponed until it is absolutely necessary, e.g.in cases with miliary or menin-geal dissemination that cannot be treated with GK radiosurgery.
