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

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.