Long-Term Outcomes of Fractionated Stereotactic Radiation Therapy for Pituitary Adenomas at the BC Cancer Agency

Abstract

To assess the long-term disease control and toxicity outcomes of fractionated stereotactic radiation therapy (FSRT) in patients with pituitary adenomas treated at the BC Cancer Agency. To ensure a minimum of 5 years of clinical follow-up, this study identified a cohort of 76 patients treated consecutively with FSRT between 1998 and 2007 for pituitary adenomas: 71% (54/76) had nonfunctioning and 29% (22/76) had functioning adenomas (15 adrenocorticotrophic hormone-secreting, 5 growth hormone-secreting, and 2 prolactin-secreting). Surgery was used before FSRT in 96% (73/76) of patients. A median isocenter dose of 50.4 Gy was delivered in 28 fractions, with 100% of the planning target volume covered by the 90% isodose. Patients were followed up clinically by endocrinologists, ophthalmologists, and radiation oncologists. Serial magnetic resonance imaging was used to assess tumor response. With a median follow-up time of 6.8 years (range, 0.6 - 13.1 years), the 7-year progression-free survival was 97.1% and disease-specific survival was 100%. Of the 2 patients with tumor progression, both had disease control after salvage surgery. Of the 22 patients with functioning adenomas, 50% (11/22) had complete and 9% (2/22) had partial responses after FSRT. Of the patients with normal pituitary function at baseline, 48% (14/29) experienced 1 or more hormone deficiencies after FSRT. Although 79% (60/76) of optic chiasms were at least partially within the planning target volumes, no patient experienced radiation-induced optic neuropathy. No patient experienced radionecrosis. No secondary malignancy occurred during follow-up. In this study of long-term follow-up of patients treated for pituitary adenomas, FSRT was safe and effective.