転移性脳腫瘍のガンマナイフ治療

Gamma-radiosurgery of Metastatic Brain Tumors

I．はじめに

　近年ガンマナイフ，あるいはlinear acceleratorを用いた，いわゆるstereotactic radiosurgery^6,7）が注目されており，特に脳動静脈奇型，その他の脳血管奇型^7,11），聴神経腫瘍^4），髄膜腫^3,5）などの治療の中で，非手術的治療法として良好な成績が報告されている．脳腫瘍では，主に良性腫瘍がその治療対象となっており，悪性グリオーマ^9），あるいは転移性脳腫瘍^{1,8,10,12,13）}などの悪性腫瘍群の治療については報告が少い．われわれは，1991年5月より，ガンマナイフによる治療を導入し，1992年12月までに約400例の治療を施行した。これらのうち，十分な経過観察が得られた転移性脳腫瘍の治療成績を検討し，本疾患がradiosurgeryの良い対象となりうるかどうか，初期効果を中心に治療効果および副作用，他の治療法の併用とその選択などについて報告する．

Twenty-six cases of various brain metastases were tre-ated with Gamma-knife. Their primary sites were : lung in 13, colon in 5, breast in 2, kidney in 2, liver in 1, ovary in 1, and a malignant melanoma. The origin of one case was not verified. There were 11 single and 15 multiple metastases. In total 70 tumors were involved. Following localization with MRI and dose planning using a compu-ter system, radiosurgery was carried out. Tumors were treated with the maximum dose between 24 and 50Gy, and with the marginal dose between 12 and 25Gy. Early follow-up results demonstrated favorable re-sponses chiefly by tumor shrinkage, central tumor necro-sis or by decreased peritumoral edema. In fact after radiosurgery, the rates of tumor shrinkage were 55.7%, 61.8% and 66.7% at 3, 6 and 9 months respectively. The tumor control rates, including regressed and stable tumors, were 98.6%, 97.1 and 85.7 at 3, 6 and 9 month in-tervals respectively.

Meanwhile, 14 cases were neurologically improved, and another 4 showed either no perceivable change. Neurological deterioration occurred in 4 cases by pro-gression of brain metastasis in 2 and by perifocal edema after radiosurgery. Recurrent brain metastases occurring after radiosurgery were treated with a repetition of Gam-ma-kinfe surgery in 4 cases, resulting in good tumor con-trol. In conclusion most of the brain metastasis can be well controlled by radiosurgery for relatively long period of time.