Abstract
Primary intracranial germ cell tumors are rare, representing less than 5% of all central nervous system tumors. Overall, the majority of germ cell tumors are germinomas and approximately one-third are non-germinomatous germ cell tumors (NGGCT), which include teratoma, embryonal carcinoma, yolk sac tumor (endodermal sinus tumor), choriocarcinoma, or mixed malignant germ cell tumor. Germ cell tumors may secrete detectable levels of proteins into the blood and/or cerebrospinal fluid, and these proteins can be used for diagnostic purposes or to monitor tumor recurrence. Germinomas have long been known to be highly curable with radiation therapy alone. However, many late effects of whole brain or craniospinal irradiation have been well documented. Strategies have been developed to reduce the dose and volume of radiation therapy, often in combination with chemotherapy. In contrast, patients with NGGCT have a poorer prognosis, with about 60% cured with multimodality chemoradiation. There are no standard approaches for relapsed germ cell tumors. Options may be limited by prior treatment. Radiation therapy has been utilized alone or in combination with chemotherapy or high-dose chemotherapy and transplant. We discuss two cases and review options for frameless radiosurgery or fractionated radiotherapy.
Highlights
BackgroundPrimary intracranial germ cell tumors (IGT) are rare, representing less than 5% of all central nervous system tumors in Western series [1,2] but may be more common in East Asia [3,4]
Elevated serum or cerebrospinal fluid (CSF) human chorionic gonadotropin (HCG) > 50 mIU/mL and/or elevated AFP are generally considered consistent with non-germinomatous germ cell tumors (NGGCT) and biopsy is not required
Germinomas have long been known to be highly curable with radiation therapy (RT) alone
Summary
Primary intracranial germ cell tumors (IGT) are rare, representing less than 5% of all central nervous system tumors in Western series [1,2] but may be more common in East Asia [3,4]. Ref = references; Pre-RT = pre-radiation therapy; HD = high definition; TPS = treatment planning system; IR = Infrared camera system with 4-6 reflectors or emitters mounted on bite-block tray; OSMS = optical surface monitoring system (AlignRT); kV = kilovoltage imaging; CBCT = cone beam CT; DOF = degrees of freedom; HD = high definition; MLC = multileaf collimator; SRS = stereotactic radiosurgery; VMAT = volumetric modulated arc therapy; FSRT = fractionated stereotactic radiotherapy; OBI = onboard imaging; GK = Gamma Knife; DCA = dynamic conformal arc; FFF = flattening fillter free; N = number; mets = metastases; OBI = on-board imager; AVM = arteriovenous malformation; CI = conformity index; HI = homogeneity index; GTV = gross target volume; PTV = planning target volume; IMRT = intensity modulate radiation therapy. An end-to-end test with older equipment utilizing 10 mm MLC leaves without 6-DOF couch advocated a GTVPTV margin of 2.8 mm [45]
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