Fractionated stereotactic radiotherapy in the treatment of pituitary macroadenomas

The use of fractionated stereotactic radiotherapy (FSRT) has evolved with technical advances in noninvasive immobilization, radiation delivery, and image guidance. The application of FSRT to pituitary tumours is aimed at reducing toxicity through improved dose conformality and reduced treatment margins. The aim of the present paper is to report our own experience and to review the published data on FSRT for pituitary macroadenomas.

Between September 2000 and October 2005, 13 patients with pituitary macroadenoma underwent FSRT at our institution. In 12 patients, radiotherapy treatment followed surgical resection (transsphenoidal resection in 8, frontal craniotomy in 3, and multiple transsphenoidal resections followed by craniotomy in 1). In 4 patients, the tumours were functional (2 adrenocorticotropic hormone-secreting, 1 prolactinoma, and 1 growth hormone-secreting); the tumours in the remaining patients were clinically non-secretory. Before radiation, 3 patients had panhypopituitarism, and 6 patients had visual field defects. All patients were treated with FSRT using non-coplanar micro-multileaf collimation portals. A median dose of 50.4 Gy (range: 45-60 Gy) was prescribed to the 76.9%-95.2% isodose surface and delivered in 1.8-Gy fractions. The median planning target volume (gross tumour plus 3 mm) was 33.5 cm3 (range: 3.2-75 cm3).

After a median follow-up of 24 months (range: 6-60 months), local control was 100%. One patient achieved clinical complete response. Treatment was well tolerated acutely for all patients. Neither radiation-induced optic neuropathy nor any radiation-related endocrine dysfunction was observed in our patients.

In accordance with published series, we found FSRT to be safe and effective in the management of large pituitary macroadenomas.