Radiotherapy in the management of giant pituitary adenomas

The description of giant pituitary adenoma is not clear yet. In this study we tried to identify which adenomas can be defined as giant pituitary adenomas when tumor control and progression free survival (PFS) are taken as end points and we also tried to evaluate prognostic factors other than tumor size.

Between January 1981 and December 1997, 74 patients with pituitary macroadenomas more than 2 cm in size were treated. Of these 30 had tumors of more than 4 cm, while 44 patients were with tumors of 2-4 cm. Two patients received primary radiotherapy, while 72 were treated postoperatively. In the postoperative group, 52 patients underwent immediate radiotherapy after surgery and 20 were treated with irradiation after regrowth or progression of the tumor after initial surgery. The mean and median tumor doses were 5518 and 5425 cGy, respectively.

Overall primary tumor control rate was 84%. The local control rates among patients with tumors more than 4 cm and among patients with tumors 2-4 cm after radiotherapy were 73 and 91%, respectively. PFS was 65% for patients who had a tumor size of more than 4 cm and 87% for the patients with tumor size of 2-4 cm (P = 0.09). Young age (<20) and tumors of unclassified histology were the bad prognostic factors. Six months after radiotherapy normalisation or improvement in hormonal hypersecretion and visual field and acuity deficits were 82 and 63%, respectively.

Tumors more than 4 cm in size may be more convenient for the definition of 'giant pituitary adenoma' when tumor control and PFS are taken as the end points.