Cyberknife stereotactic treatment of pituitary adenomas: A single center experience using different irradiation schemes and modalities

Background: Stereotactic irradiation is proposed for treatment of pituitary adenomas (PAs) in patients with tumor progression/recurrence after surgery and in cases not eligible for other therapies. In the literature several papers have been published on the role of the Gamma-Knife stereotactic irradiation for management of PAs, but data on the role of stereotactic Cyberknife (CK) are still limited. We describe a single-center experience using CK stereotactic radiosurgery (CK-SRS) and hypofractionated radiotherapy (CK-SRT) for PAs treatment, analyzing its efficacy/safety in the light of current literature. Methods: We retrospectively collected clinical data from PAs patients treated using CK system at the University Hospital of Messina, Italy, between 2008 and 2018. The efficacy was evaluated by analyzing the tumor growth/biochemical disease control rates, and the safety by evaluating post-treatment pituitary and/or visual deficits. Results: Twenty-four PAs patients were included in the study. The mean follow-up was 42.21 ± 32.67 months. The overall tumor growth control rate was 91.6%, but it was higher using the single-session scheme (100%) than using hypofractionated sessions (80%). The biochemical disease control rate was 60%, but increased to 80% in GH-secreting PAs. Post-treatment hypopituitarism occurred in 41.66% of cases, being 35.71% using a hypofractionated scheme, and 50% using a single-session treatment. No cases of post-treatment visual deterioration were observed. Overall and progression-free survival were respectively 84.6% and 83.6% at three years. Conclusions: Cyberknife irradiation is an effective and safe option for PAs treatment, being associated to an excellent tumor growth/biochemical control of the disease, and to a low rate of post-treatment complications. The efficacy seems to be higher when using a single-session scheme even if this could be associated to a higher incidence of post-treatment hypopituitarism. Keywords: Cyberknife, Pituitary adenomas, Radiosurger