Radiation therapy for intracranial germ cell tumors.
Although radiation therapy (RT) is essential to the management of intracranial germ cell tumors, the ideal radiation dose and field remain controversial. For the treatment of germinoma, whole central nervous system radiation, which was once the standard RT field, is being replaced by whole ventricle (WV) field radiation for localized disease. The use of induction chemotherapy has been expected to further reduce the RT field and dose; however, use of a localized field smaller than the WV field has resulted in a higher recurrence rate. Therefore, the WV field should be considered appropriate even after induction chemotherapy. With regard to the radiation dose to the primary tumor site, it can be reduced to 40-45 Gy in RT alone. The further reduction of the radiation dose when using a combination of chemotherapy and RT is yet to be determined. Unlike germinomas, nongerminomatous germ cell tumors, with the exception of mature teratomas, are refractory to conventional RT. The whole central nervous system field should thus be used for all but immature teratomas. Given that local progression is the primary pattern of recurrence even after effective induction chemotherapy, RT dose increase through the use of modern techniques, including stereotactic irradiation and intensity-modulated RT, should be investigated.
Aoyama
Hidefumi
H