Suprasellar germinomas; relationship between tumour size and diabetes insipidus

The clinical and neuro-endocrinological aspects of 17 suprasellar germinoma patients treated between 1972-1991 are reported. Surgical extirpation was not initially attempted, but all patients received irradiation with or without a biopsy. Sixteen of those have led useful lives with appropriate hormonal replacement therapy during a mean follow up of 8 years. Seven tumours at diagnosis were less than 2 cm in diameter (type 1), nine tumours more than 2 cm (type 2), and one double midline tumour was of unknown size. All 7 type 1 patients required 1-deamino-8-D-arginine-vasopressin (DDAVP) to control diabetes insipidus (DI), but only 2 of the 9 type 2 patients have needed DDAVP since completion of the treatment. Patients with smaller tumours required more DDAVP following tumour disappearance, than those with larger tumours. The prognostic indicators for the post-treatment course of DI and retarded growth appeared to be the tumour size and the age at diagnosis. We also emphasize the absence of metastasis in unoperated cases and the use of tumour markers as a diagnostic criterion which obviates surgical acquisition of tissue to make the diagnosis. Possible reasons are discussed and the literature reviewed.