上咽頭癌に対するガンマナイフ治療の試み

Gamma-knife Radiosurgery of Epipharyngeal Cancer:Report of a Case

　はじめに

　上咽頭部に発育する腫瘍の中で，上咽頭癌は通常手術的摘出が不可能であるため，化学療法の他，放射線外照射あるいは腔内照射が行われている。放射線感受性は高く初期には比較的良好な反応が認められるものの，長期生存例は少なく，5年生存率は30〜45％とされ，いま十分な成果が得られていない。ガンマナイフは主に頭蓋内病変の定位的放射線治療（radiosurgery）を目的にスウェーデンのLeksell^1）により開発された装置であるが，眼窩，頭蓋底，鼻咽頭病変への適応が可能である。今回，当病院に新たに導入したガンマナイフにより，上咽頭癌を治療する機会を得たので，ここに紹介する。

The first experience of gamma-radiosurgery of epipharyngeal cancer is reported. A 64-year-old man with epipharyngeal cancer since 1987 treated with a full dose of external irradiation (60Gy), intracavitary irradiation with Co-60 (20Gy) and cisplatin-based chemotherapy, visited our hospital because of the tumor recurrence. A small tumor, 10 mm in diameter, was found in the right epi-pharynx. The first radiosurgery with Gamma-knife was carried out in U.S.A. on Jan. 1990. A dose of 40 Gy at the center with 20 Gy at the tumor margin was given. After 5 months of remis-sion a new tumor appeared in the left epipharynx, which demonstrated a marked progression with protrusion into the cavity as well as invasion to the clivus. The second radiosurgery with Gamma-knife was done in our hospital on July 1991 and the dose of 25Gy at the center with 10Gy at the tumor margin was delivered to the tumor, appro-ximately 55mm in its diameter. He has been well subsequently and MRI disclosed a marked shrin-kage of the tumor with clinical improvements one month later. In conclusion it is possible to treat epipharyngeal tumor with radiosurgry at least as adjuvant therapy or as solely curative procedure when the tumor is small and well localized.