Gamma Knife Pituitary Radiosurgery for Refractory Metastatic Bone Pain: A Single-Centre Retrospective Palliative Case Series

INTRODUCTION: Intractable cancer-related pain, particularly from metastatic bone disease, can be severe and refractory to conventional treatments. Gamma Knife pituitary radiosurgery (GKPR), which delivers a high dose of focused radiation to the neurohypophysis, has emerged as a potential minimally invasive palliative option for refractory cancer pain. We report short-term clinical observations from a single-centre retrospective case series of GKPR in patients with treatment-resistant metastatic bone pain. METHODS: We retrospectively reviewed four adult patients with intractable cancer-related bone pain who underwent GKPR between year 2023-2024. All patients had partial but inadequate response to opioids and other conventional pain treatments prior to GKPR, Karnofsky Performance Status (KPS) >40% and no prior history of cranial irradiation. GKPR was performed targeting the neurohypophysis using a maximal dose of 140Gy. Pain relief was assessed using a visual analogue scale (VAS) at pre- and post-radiosurgery, as well as during regular follow-ups. A >50% reduction from baseline pain score was defined as clinically meaningful pain relief. Analgesic requirements and short-term procedural related adverse events were recorded. Formal endocrinological assessment were not routinely performed in asymptomatic patients due to palliative intention. RESULTS: A total of four patients with refractory metastatic bone pain secondary to various primary malignancies were included. Baseline VAS score ranged from 8 to 10 (median 9) and KPS ranged from 60% to 90% (median 60%). Three out of four patients (75%) achieved clinically meaningful pain relief following GKPR. The onset of pain reduction >50% occurred between 1 to 14 days post-treatment (median 2 days). A modest reduction in opioid consumption was observed, with a median 14% reduction of daily morphine-equivalent dose and none required escalation of analgesic medications. Pain improvement was sustained throughout the available follow-up period, with a median duration of 2.5 months (range 0.5-10 months). No immediate procedure-related complications were observed during the follow-up period. CONCLUSION: In this small retrospective palliative case series, GKPR was associated with rapid short-term pain reduction in selected patients with refractory cancer-related bone pain without immediate procedure-related complications. Given the limited sample size, short follow-up duration inherent to the palliative setting and absence of systematic endocrine evaluation, conclusions regarding long term durability or safety cannot be drawn. Nonetheless, these observations suggest that GKPR may represent a feasible, minimally invasive, palliative option for carefully selected patients, warranting further prospective investigations.