悪性神経膠腫におけるBrachytherapy後の再発様式の検討

Patterns of Recurrence in Malignant Gliomas after Brachytherapy

I．はじめに

　悪性神経膠腫は種々の積極的な治療にもかかわらず，早晩再発をきたし，患者を死に到らしめる極めて予後不良の疾患であるが，その再発は約80％以上が局所再発であり^6,10），本疾患の治療における局所制御の重要性が指摘されている^5,19）．われわれは1987年より各種の悪性脳腫瘍に対し，¹⁹²Iridiumを用いた放射線組織内照射（brachytherapy）を施行しており，その有用性を報告してきた^9,13,14）．しかしながら，症例を重ね，長期経過観察を行っていく中で，本治療により局所再発が減少し，症例全体としては予後の改善を認めたものの，一部に原発巣がよく制御されているにもかかわらず髄腔内播種の形で再発する症例を経験するようになった．今回，この観点からbrachytherapy後の再発様式を検討したので若干の文献的考察を加え報告する．

More than 80% of malignant gliomas have been re-ported to recur locally after conventional chemo-radiation therapy. This regional pattern of recurrence has encouraged the introduction of new treatments for local tumors. Since 1987 interstitial brachytherapy using Iridium-192 seeds has been carried out in our depart-ment for malignant brain tumors. The present study was designed to evaluate the patterns of recurrence fol-lowing interstitial brachytherapy and to assess how this recurrence differs from that observed in patients treated by conventional means.

Ten patients who satisfied the following criteria were selected among 41 patients treated with brachytherapy. The criteria were; 1) histologically diagnosed to be malignant glioma (astrocytoma grade Ⅲ or glioblas-toma), 2) followed up with MRI every month after the brachytherapy, 3) follow-up period was more than 6 months, and 4) the time of recurrence was confirmed. The patients were classified into 3 groups according to the patterns of tumor recurrence as follows; 1. Local re-currence group: The tumor recurred near the pretreat-ment tumor site. 2. Necrotomy group: Reoperation was performed because of neurological deterioration and radiographic evidence of increasing mass effect with surrounding edema. Neurological symptoms were un-changed or improving during the 6 months after the reoperation. 3. CSF seeding group: Primary tumor was well controlled, but seeding via cerebrospinal fluid was recognized on MRI.

Local recurrence occurred in three patients, necro-tomy was carried out in three patients, and CSF metas-tases were defined by both MRI and clinical symptoms in four patients. Median radiation does was 33 Gy in the local recurrence group, 57.6 Gy in the necrotomy group, and 43.2Gy in the CSF seeding group. As six patients are still alive, no statistical difference in the survival was found among these groups. The interval from the diagnosis to the recurrence tended to be lon-ger in the CSF seeding group than in the other groups. These results indicate that brachytherapy may im-prove local control and make local recurrence less like-ly, but improved local control allows development of CSF seeding. Effective therapy for controlling CSF