Optimization of Intracranial Germinoma Treatment: Radiotherapy Alone with Reduced Volume and Dose.

Purpose: We investigated optimal management for intracranial germinoma, including target volume and dose of radiation therapy (RT) and the combination of RT and chemotherapy (CTx).

Methods And Materials: We retrospectively evaluated 213 patients with intracranial germinoma treated between 1971 and 2017. Treatment policies changed as diagnostic techniques and clinical experience improved. In the 1980s, trial RT and tumor marker study were performed, and craniospinal irradiation was performed to treat patients with presumed germinoma. CTx was introduced in 1991, and RT volume was reduced in patients showing a complete response. In 2012, the policy was changed to a "reduced volume/dose RT alone" approach, involving a smaller target volume (the whole ventricle/whole brain for localized disease) without CTx. RT doses were gradually reduced to 36 Gy for primary tumors and 18 Gy for neuraxis.

Results: The median age was 16 years. In total, 118 and 95 patients had pathologically proven and presumed germinoma, respectively, and 151 and 62 patients had localized and multifocal or metastatic diseases, respectively. With a median follow-up of 141 months, the 10-year disease-free and overall survival rates were 91.6% and 95.6%, respectively. Recurrence rates were similar for patients receiving RT-only (9 of 137, 6.6%) and those receiving CTx + RT (4 of 73, 5.5%); all patients receiving CTx-only experienced recurrences (3 of 3, 100%). Rates were the highest in the focal RT group (10 of 29, 34.5%) but were relatively low in the whole ventricle/whole brain RT (3 of 51, 5.9%) and craniospinal irradiation groups (0 of 130, 0%). Infield failure occurred in 3 patients. Fourteen patients died of recurrence (n = 4), secondary malignancy (n = 4), CTx-related toxicity (n = 2), and others (n = 4). Among the 33 patients who received "reduced volume/dose RT alone" treatment, 2 (6.1%) experienced recurrence in the spinal cord and biopsy tract, respectively.

Conclusions: The additional benefit of CTx in the treatment of intracranial germinoma seems minimal. An RT-only approach with reduced target volume and dose seems reasonable.