Long-term outcomes of adjuvant proton radiotherapy for residual pituitary adenoma in adults

Fabian J. K. et al. 

This retrospective single-institution study evaluated the long-term efficacy and toxicity of adjuvant proton radiotherapy (PRT) in 22 adults with residual pituitary adenomas (PAs) after subtotal resection. Most patients had complex macroadenomas with suprasellar and cavernous sinus extension, frequently involving the optic apparatus and carotid arteries, making further surgery or stereotactic radiosurgery unsuitable. Sixteen patients had non-functioning adenomas and six had functioning adenomas. PRT was delivered using active raster scanning, with a median dose of 52.2 Gy(RBE) for non-functioning and 50.4 Gy(RBE) for functioning adenomas, generally in 28 fractions. After a median follow-up of 65 months, 3- and 5-year local control rates were 100%, with radiographic tumor regression in all patients. Hormonal control in functioning adenomas was also 100% at 3 and 5 years. Visual outcomes were favorable, with subjective improvement reported by 64% of patients and no patient-reported deterioration. Toxicity was predominantly mild and acute, mainly fatigue and headache. Only one patient developed new secondary hypopituitarism.

In conclusions, adjuvant PRT provided excellent long-term tumor and hormonal control with limited toxicity in patients with complex residual PAs. Its dosimetric advantages may be particularly valuable for large, irregular adenomas close to critical neurovascular structures. These findings support PRT as a safe and effective option in selected patients unsuitable for further surgery or stereotactic treatment, although larger prospective studies are required to confirm its long-term benefits.

Published by Journal of Neuro-Oncology 2026.
https://doi.org/10.1007/s11060-026-05669-2