Reduced-dose Radiotherapy without Chemotherapy for Intracranial Germinomas: Results from an Asian Multicenter Study.

Abstract

Background: Long-term efficacy data supporting the use of reduced-dose radiotherapy (rdRT) alone for intracranial pure germinoma remain limited. In this study, we evaluated the long-term efficacy and safety of rdRT alone in patients with this condition.

Methods: We retrospectively analyzed the data of 139 patients with intracranial pure germinoma treated with RT alone, using whole-ventricle irradiation (73.6%), whole-brain irradiation (9.3%), or craniospinal irradiation (CSI, 17.1%). Patients who had M+ disease were included, whereas those treated with local RT alone were excluded. The most commonly prescribed dose to gross tumors was 30.0-30.6 Gy delivered in 15-17 fractions (median total dose, 35.5 Gy). The median extended-field (whole-ventricle, whole-brain, or craniospinal) dose was 23.4 Gy. Survival outcomes were analyzed according to total RT dose, whole-ventricle dose, RT field, and disease distribution.

Results: At a median follow-up of 102 months, the 5- and 10-year event-free survival (EFS) rates were 90.0% and 88.4%, respectively, and the corresponding overall survival rates were 100.0% and 98.4%. Dose escalation beyond 30.6 Gy did not improve EFS (P = 1.000). A whole-ventricle dose of 18 Gy was not associated with inferior EFS compared with >18 Gy (P = 0.155). In patients with bifocal disease (suprasellar and pineal, n = 24), CSI significantly improved 5-year EFS (100.0% vs. 63.3%, P = 0.040). In the study-defined optimal RT group (total dose ≥30 Gy, excluding bifocal disease without CSI; n = 125), the 3- and 5-year EFS rates were 94.2% and 92.4%, respectively. No grade ≥3 acute or late RT-related toxicities or secondary malignancies were observed.

Conclusions: RdRT alone, administered with an appropriate dose and RT field according to disease status, provided excellent long-term tumor control with minimal toxicity. Tumor and extended-field doses of 30.6 Gy and 18 Gy, respectively, appeared adequate. A prospective phase 2 trial is planned to further validate this treatment strategy.