サイバーナイフ治療の現況と展望

CyberKnife Radiosurgery : Present Status and Future Prospect

はじめに

　サイバーナイフ®(CyberKnife®：CK）は，ロボット誘導型定位放射線治療器と称されるように，コンピュータの発達によって進歩したロボット工学とコンピュータ画像デジタル処理技術，小型リニアックを統合した定位放射線照射システムで，1994年Accuray社（USA）によって開発され，スタンフォード大学において脳神経外科医John Adler博士のもと治療が開始された^1）。1997年，わが国に第1号機が山口県の厚南セントヒル病院に導入され，1998年に保険適応となった。2010年9月現在，世界で207台，わが国で22台が稼働している（Fig.1，2）。

　2001年，米国食品医薬品局（Food and Drug Administration：FDA）がCKを体幹治療器と認定し，世界標準のCKは全身治療器として稼働しており，頭蓋内病変や頭頸部癌以外に脊髄病変，肺癌，肝臓癌，膵臓癌，前立腺癌などに対してCK治療が行われている。

　わが国では，2008年6月12日に医薬品医療機器総合機構（Pharmaceuticals and Medical Devices Agency：PMDA）から体幹治療器として薬事承認され，同年12月に保険収載され，ようやく世界標準のCKに追いついた。

　本稿では，CKの構造上の特徴と治療の概略に触れ，今後の展望について述べることとする。

Abstract

　The CyberKnife Robotic Radiosurgery System is a non-invasive alternative to surgery for the treatment of both cancerous and non-cancerous tumors anywhere in the body, including the prostate, lung, brain, spine, liver, pancreas, and kidney.　The treatment, which involves the delivery of high doses of radiation to tumors with extreme accuracy, offers new hope to patients who have inoperable or surgically complex tumors or who may prefer a nonsurgical option.　To date, more than 95,000 patients have been treated and more than 207 systems have been installed worldwide.

　The CyberKnife System is a one-of-a-kind device because of the following reasons.

　First, the CyberKnife System uses image guidance software to track and continually adjust treatment for any patient or tumor movement.　This advantage places the system far ahead of other similar treatments.　It allows patients to breathe normally and relax comfortably during treatment.

　Second, some forms of radiosurgery require rigid head frames that are screwed into the patient's skull in order to minimize any head movement.　The CyberKnife System does not require such extreme procedures to maintain the head position; instead, it relies on the sophisticated tracking software, allowing for a much more comfortable and noninvasive treatment.

　Third, unlike some radiosurgery systems, which can only treat tumors in the head, the CyberKnife System has unlimited reach to treat a broad range of tumors throughout the body, including the prostate, lung, brain, spine, liver, pancreas, and kidney.

　Finally,the CyberKnife System's treatment accuracy is unrivaled.　Its ability to treat tumors with supreme accuracy is noncomparable to that of other radiation therapy and radiosurgery systems.　The CyberKnife System can essentially "paint" the tumor with radiation,allowing it to precisely deliver treatment to the tumor alone,sparing surrounding healthy tissue.