脳血流からみたGerm-cell tumorの放射線療法による晩期影響

DELAYED EFFECTS OF RADIATION ON PATIENTS WITH GERM-CELL TUMOR, WITH SPECIAL TO CEREBRAL BLOOD FLOW

　放射線療法（RT，39.6〜60Gy平均47.5Gy）後1〜14年の観察期間において再発がみられなかった20例のgerm-cell tumor（germinoma17例）を対象にその晩発障害を分析する目的から，平均脳血流量（m CBF，¹³³Xe吸入法により測定）を中心に，脳萎縮の度合，心身の発達・社会適応性を検討した。対象はRTを受けた年齢によって，8〜15歳〔C群〕と17〜28歳〔A群〕の2群に分けられた。CBFの低下は全体の8例40％にみられ若年者程その傾向は強かったが，総線量との間で有意な相関はなかった。一方，照射容積線量（IVD）とCBFとは，C群のみに統計的有意な1次回帰直線が成立した。脳萎縮は全体の12例60％にみられた（C群66.7％，A群50％）。全例身体の発達は良好であったが，記銘力低下のみが6例30％にみられた。総線量，IVD，またはmCBFと脳萎縮，記銘力低下との間に有意な相関はなかった。小児期におけるCBFは照射線量に照射野の因子を加えたIVDと密接な関係を有していると思われた。

Delayed effects of radiation therapy (RT) on twenty patients with germ-cell tumors, including 17 cases of germinoma, were evaluated with special reference to cerebral blood flow (CBF). All pati-ents except for one of germinoma had craniotomy to verify the tumor histology, then RT followed with a total dose of 39. 6 to 60 Gy for each patient. A follow-up study with CT scans and MRI proved not any recurrence of the tumors during the past 14-year period between June, 1975 and April, 1989.

On the other hand, CBF was measured by ¹³³Xeinhalation 1 to 14 years after RT. 40% of all pa-tients were below critical values of CBF with hig-her frequency in the younger. Statistically, the postirradiated changes of CBF were not related to a total administered dose, grading of brain atro-phy, or physical mental developments, but closely related to irradiated volume dose (product of ab-sorbed dose and field, rad･cm³) only for the age ranging from 8 to 15 years at RT.

These results suggested that late effects of RT on CBF were more strongly depend upon absorbed dose and field of irradiation to brain in children than in adolescents.