Abstract: Background and purpose: The intracranial germ cell tumors always sensitive to radiotherapy and chemotherapy. However, in certain cases, definitive diagnosis before treatment is not conceivable due to the absence of pathological biopsy examination. Therefore, a therapeutic consensus on dealing with these patients remains to be established. The aim of this study was to evaluate the clinical significance and effectiveness of the diagnostic lowdose radiotherapy plus chemotherapy in intracranial germ cell tumors. Methods: There were 28 patients (12 male patients, 16 female patients, medium age 14.5 years) enrolled in this study. They had normal levels of α-fetoprotein (AFP) and β-human chorionic gonadotropin (β-HCG). Magnetic resonance imaging (MRI) showed typical images of intracranial germ cell tumors at suprasellar and pineal gland regions. Clinical examination also strongly supported the intracranial germ cell tumors diagnosis. We used diagnostic radiotherapy combined with chemotherapy for these patients because stereotactic or surgical biopsy was excluded or refused. These patients received an initial phase of low-dose diagnostic radiotherapy (3.4 Gy/1.7 Gy/2 F), then MRI was performed. The following treatment depended on the MRI results: ⑴ For the patients showing stable disease (SD), surgery was recommended. ⑵ For those showing complete remission (CR) or partial remission (PR), chemotherapy (VP16+DDP regime) was given for 2 weeks. The rest of the patients showing CR received further intensity-modulated radiation therapy (IMRT) or three-dimensional conformal radiotherapy (3D-CRT). The treatment varied accordingly with local irradiation, or whole brain irradiation plus whole ventricular irradiation then boost, or whole brain irradiation with local intensitymodulated irradiation (total doses≤50.4 Gy at pineal gland region; ≤41 Gy at sellar region). ⑶ If the patients failed to achieve CR after chemotherapy, surgery was recommended. Results: One patient showed SD after diagnostic radiotherapy and the tumor was surgically removed. The presence of a pituitary tumor was found. Another patient remained PR after diagnostic radiotherapy + chemotherapy and the tumor was also surgically removed. The presence of a mixed immature pituitary tumor was found. Twenty-six patients showed CR after low-dose diagnostic radiotherapy and chemotherapy. They received the second phase radiotherapy (IMRT or 3D-CRT). All of the 28 patients were followed up for 1-8 years. They survived well and no relapse occurred. Furthermore, no obvious sign of radiation-induced damage was observed. Conclusion: Low-dose radiotherapy combined with chemotherapy demonstrated convincing efficiency to make a distinction between true and false germinoma. This method can be safely used in clinic to treat the patients with clinically diagnosed intracranial germ cell tumor without biopsy confirmation.

Key words: Intracranial germ cell tumors, Germinoma, Diagnostic radiotherapy, Chemotherapy