Radiotherapy for nonfunctional pituitary adenoma: analysis of long-term tumor control

Object. The authors studied outcomes in patients who had undergone radiothe rapy for nonfunctional pituitary adenoma to assess long-term tumor control and to identify factors affecting tumor control such as higher radiation do ses, improved imaging, and histological characteristics of the tumor. Methods. In this retrospective study, the authors evaluated 120 patients wh o received radiotherapy for nonfunctional pituitary adenomas between 1960 a nd 1991. The median follow-up period was 9 years (range 1 month-32 years). Radiation doses varied between 37.6 and 65.6 Gy (median 46.7 Gy). Tumors progressed in 15 of the 120 patients by 1 to 25 years after radiothe rapy. Actuarial tumor control rates at 10, 20, and 30 years were 87.5 +/- 3 .6%, 77.6 +/- 6.3%, and 64.7 +/- 12.9%, respectively.Tumor progression afte r radiotherapy occurred significantly more often (p = 0.0397) in patients w ith oncocytoma than in patients with nononcocytic nun cell adenoma. No othe r factors correlated significantly with tumor control. One case of optic an d oculomotor neuropathy developed 4.5 years after a maximum dose of 50 Gy i n 25 fractions. Radiation-induced neoplasms (meningioma and glioblastoma mu ltiforme) developed at a rate of 2.7% at 10 and 30 years. Conclusions. The oncocytic variant of null cell pituitary adenoma appears l ess sensitive to control by radiotherapy than nononcocytic undifferentiated cell adenoma. A follow-up period extending beyond 20 years is needed adequ ately to assess the efficacy of radiotherapy for tumor control. Doses of 40 or 45 Gy in 20 or 25 fractions, respectively, appear optimal.