AbstractBackground and objectivesRecurrence is frequent in surgically treated non-functioning pituitary adenomas (NFPA). The use of radiation therapy (RT) to prevent recurrence has to be weighted against the potential side effects, particularly, hypopituitarism. Our objective was to evaluate the efficacy and safety of RT in postoperative patients with NFPA with adenoma remnant.Patients and methodsThe 3- and 5-year outcome of 51 patients with NFPA with a remnant after surgery that received RT (cases) was compared with that of 61 subjects who did not receive RT (controls). Cases and controls were matched for postoperative remnant size, cavernous sinus invasion, age and gender.ResultsTumour volume decreased in the radiated group from a median of 1,601 mm³ to 816 mm³ after 5 years of follow-up (p = 0·01, 50% tumour volume reduction). In the non-radiated controls median tumour volume decreased at 3 years but increased again after 5 years (baseline 1,415 mm³, 5 years 1,204 mm³, p = 0·93). Recurrence rate was 4% for the radiated group and 29% for the controls (OR 0·10, 95% CI 0·01–0·04, p = 0·02). Although pituitary hormone deficiencies at baseline were more prevalent in the radiated group, after 5 years, both groups showed a significant worsening of pituitary function. No RT-related side effects were recorded.ConclusionPostoperative RT is effective in preventing tumour regrowth in NFPA patients with postoperative remnants. The fact that hypopituitarism is highly prevalent even in non-radiated patients should allow a more generalised use of this treatment modality.