P08.22THE ROLE OF CYBERKNIFE FOR PITUITARY METASTASES

BACKGROUND: Pituitary metastases are found in 1.0-26.7% of cancer patients at autopsy. But clinically very rare. We evaluate the efficacy and safety of CyberKnife treatment in the management of metastatic cancer to the pituitary grand. PATIENTS 13 pituitary metastases (male 6, female 7). Age 47y-69y (median 53y). KPS ≧70. No previous irradiation. METHODS: Treatment system: CyberKnife (G3 or G4), Planning system: On target, Multiplan (Accuray), Calculation model: Ray tracing, Inverse algorithm, Immobilaization: thermoplastic mask, Image: CECT 1mm in thickness + MRI Gd T1WI 1-3mm in thickness, PTV = CTV = GTV, Verification: TLS (Target locating system), 6 axis correction. TREATMENT PROTOCOL: Marginal dose: D95PTV ≧ 95%, iso-dose line 80% (goal), Fractions: tumor size, adjacent to OAR (organs at risk), Tolerable dose of optic appratus: 12Gy (SRS), 21Gy (3fr.), 25Gy (5fr.), 28Gy (7fr.). Tumor volume (PTV): 0.5-18.2 cc (median 2.8 cc), Primary origin: Breast 5, Lung 2, Others 6. Clinical symptom: visual disturbance 11 (85%), diabetes insipidus 5 (38%), diplopia 1 (7.7%), asymptomatic 1 (7.7%). Marginal dose: 18-35 Gy (median 23Gy). RESULTS: Follow up periods 4-31months. Progression free survival: 81.8% (@6m), 63.6% (@12m), 54.5% (@24m). Overall survival: 92.3% (@3m), 84.6% (@6m), 67.3% (@12m), 25.6% (@24m). Maximum dose for optic apparatus BED2 (Gy): 84-229 Gy (median 98.3Gy). Only 1 case became entirely blind 12 months after CyberKnife for 6 months until her death, despite tumor reduction. In this case, maximum dose for optic apparatus BED2 (Gy) was 229 Gy (highest). CONCLUSION: These preliminary results seem to indicate that CyberKnife SRT is a safe, effective and palliative treatment for most patients with pituitary metastasis. To prevent radiation induced optic neuropathy, maximum dose for optic apparatus BED2 (Gy) is under 126 Gy (single dose equivalent: 15Gy). Its safety and efficacy remain to be observed in long-term follow up.