Radiation Therapy

CNS germinomas are highly radiosensitive and have been traditionally treated successfully with radiation therapy alone. Historically, patients with nondisseminated disease have been treated with craniospinal irradiation plus a boost to the region of the primary tumor. The dose of craniospinal irradiation has ranged from 24 Gy to 36 Gy, although studies have used lower doses. The local tumor dose of radiation therapy has ranged between 40 Gy and 50 Gy. Studies of lower-dose craniospinal irradiation have shown excellent outcomes.[19] This modification has resulted in 5-year OS rates exceeding 90%.[20]; [21][Level of evidence B4]; [22,23][Level of evidence C1] These excellent survival rates have allowed investigators to focus on reducing the radiation treatment volume and dose in an attempt to decrease late effects.[21,24,25]

Patterns of relapse after craniospinal irradiation versus reduced-volume radiation therapy (whole-brain or whole-ventricular radiation therapy) have supported the omission of craniospinal irradiation for localized germinomas.[26-28] On the basis of these results, the treatment for patients with localized germinomas has been modified to cover the whole ventricular system (24 Gy) followed by a boost to the primary site (30–40 Gy), rather than to deliver radiation therapy to the entire craniospinal axis or even to the whole brain. This change has not resulted in worse outcomes and is expected to minimize the acute and long-term toxicity of radiation therapy. Focal radiation therapy directed only to the tumor volume, even after neoadjuvant chemotherapy, results in ventricular relapses; therefore, focal radiation therapy is not recommended.[25]