Revised: June 2014
1. Pineal Region Germ Cell Tumours
Tumours of all types of germ cell origin may arise in the pineal region: germinoma, embryonal carcinoma, dermal sinus tumour, choriocarcinoma, teratoma. It may be possible to make a clinical diagnosis of pineal germ cell tumour in the absence of histology from biopsy: pineal mass in a young patient, usually male, with elevation of serum or CSF tumour markers (AFP + / - HCG).
Because of a high propensity for dissemination within the CSF, MRI staging of the whole of the craniospinal axis is important prior to treatment.
Germinomas are exquisitely radiosensitive. Craniospinal radiation is required for disseminated disease. For localized germinoma, whole ventricular radiation (21-24 Gy) with a boost to the tumour site (40-45 Gy) is recommended (1). The addition of chemotherapy in localized germinoma has not reliably led to a reduction in RT does or volume and should be considered as part of randomized trials.
Non-germinomatous germ cell tumours (NGGCT) are less radiosensitive than pure germinoma. Craniospinal irradiation is recommended for disseminated disease and is controversial with localized NGGCT. Because most radiotherapy regimens are associated with a high failure rate, platinum containing chemotherapy regimens are often used prior to radiotherapy. There are current studies designed to look at reducing CSI fields and doses in patients that achieve a complete response to neoadjuvant chemotherapy.
Reference:
1. Haas-Kogan DA, Missett BT, Wara WM, et al. Radiation therapy for intracranial germ cell tumors. Int J Radiat Oncol Biol Phys 2003; 56:511.
2. Craniopharyngioma
Craniopharyngiomas are histologically benign tumours arising in the sellar and suprasellar regions from embryonic squamous cell rests of the pharyngeal-hypophyseal duct. Investigations show a cystic, solid or mixed mass lesion associated typically with calcification.
These lesions are slow growing and may be large by the time they present with endocrine dysfunction (80 - 90%), visual problems or signs of raised intracranial pressure.
The optimum management for these tumours is controversial. Initial surgical resection and cyst decompression is almost always attempted. Management strategies may include radical surgery alone for small lesions, subtotal resection followed by planned post-operative radiotherapy or primary radiation therapy alone. There is evidence to show that subtotal resection and planned post-operative radiotherapy may have less associated morbidity than aggressive surgical intervention (1)and an improved chance of local control (2).
References:
Sanford RA. Craniopharyngioma: results of survey of the American Society of Pediatric Neurosurgery. Pediatric Neurosurgery. 21 Suppl 1:39-43, 1994.
Hetelekidis S. Barnes PD. Tao ML. Fischer EG. Schneider L. Scott RM. Tarbell NJ. 20-year experience in childhood craniopharyngioma. International Journal of Radiation Oncology, Biology, Physics. 27(2):189-95, 1993 Sep 30.
3. Chordoma
Chordomas are slow-growing tumours arising from the notochord that forms the early embryonal axial skeleton. The vast majority arises from the spheno-occipital area (35%) and from the sacrococcygeal region (50%) (1). Local invasion is the predominant mode of tumour extension; metastasis occurs infrequently and usually is associated with the late stages of tumour evolution.
Due to its locally aggressive nature, complete surgical removal is usually not amenable. Nonetheless, the best local control results published consist of partial resections with advanced skull base surgical techniques followed by proton beam irradiation (2). The latter enables a high dose of radiation deposited in the tumour while minimizing irradiation of adjacent normal critical structures. During follow-up, most will not show any significant decrease in the size of the tumour volume. The tumour is considered controlled if there is no progression on clinical and radiologic grounds.
References:
Heffelfinger M, Dahlin D, MacCarty C, et al: Chordomas and cartilaginous tumors at the skull base. Cancer 32:410-420, 1973
Munzenrider J, Liebsch N, Efird J : Chordoma and chondrosarcoma of skull base: treatment with fractionated x-ray and proton radiotherapy. Head and Neck Cancer, Volume 3:649-654, 1993.
