Occurrence of pituitary hormone deficits in relation to both pituitary and hypothalamic doses after radiotherapy for skull base meningioma.

CONTEXT

Little accurate information is available regarding the risk of hypopituitarism after irradiation of skull base meningiomas.

DESIGN

Retrospective study in a single centre.

PATIENTS

48 patients with a skull base meningioma and normal pituitary function at diagnosis, treated with radiotherapy (RXT) between 1998 and 2017 (median follow-up of 90 months).

MEASUREMENTS

The GH, TSH, LH/FSH and ACTH hormonal axes were evaluated yearly for the entire follow-up period. Mean doses delivered to the pituitary gland (PitD) and the hypothalamus (HypoD) were calculated, as well as the doses responsible for the development of deficits in 50% of patients after 5 years (TD50).

RESULTS

At least one hormone deficit was observed in 38% of irradiated patients and complete hypopituitarism in 13%. The GH (35%), TSH (32%) and LH/FSH axes (28%) were the most frequently affected, while ACTH secretion axis was less altered (13%). The risk of hypopituitarism was independently related to planning target volume (PTV) and to the PitD (threshold dose 45 Gy; TD50 between 50 and 54 Gy). In this series, the risk was less influenced by the HypoD, increasing steadily between doses of 15 and 70 Gy with no clear-cut dose threshold.

CONCLUSIONS

Over a median follow-up period of 7.5 years, hypopituitarism occurred in more than one third of patients irradiated for a skull base meningioma, and this prevalence was time- and dose-dependent. In this setting, the risk of developing hypopituitarism was mainly determined by the irradiated target volume and by the dose delivered to the pituitary gland.