Efficacy and Toxicity of CyberKnife-M6 BasedStereotactic Radiotherapy in Patients with Uveal Melanoma
iARTIST-International Advanced Radiotherapy Techniques Symposium, İstanbul, Türkiye, 11 - 14 Haziran 2026, (Tam Metin Bildiri)
- Yayın Türü: Bildiri / Tam Metin Bildiri
- Basıldığı Şehir: İstanbul
- Basıldığı Ülke: Türkiye
- Bursa Uludağ Üniversitesi Adresli: Evet
Özet
PURPOSE To evaluate the efficacy and dosimetric outcomes of stereotactic radiotherapy (SRT) delivered using the CyberKnife-M6 (CK-M6) system in patients with uveal melanoma (UM). MATERIALS AND METHODS Between 2019 and 2025, twelve patients with radiologically diagnosed UM were treated. Magnetic resonance imaging (MRI) with a 1-mm slice thickness was obtained for all patients. Immobilization was achieved using a non-invasive mask. The eye was fixed with retrobulbar anesthesia, computed tomography (CT) simulation images were acquired, and subsequently fused with MRI. The planning target volume (PTV) was generated by adding a 0–1 mm margin to the gross tumor volume (GTV), and organs at risk were contoured. Treatment plans were created using either fixed or multileaf collimators. Retrobulbar anesthesia was applied before each fraction. Patients were followed every three months with orbital MRI, ocular ultrasonography, and fundoscopic examination. Toxicities were reported according to CTCAE version 5.0. RESULTS The median follow-up time was 22 months (8–52). Four patients were female and eight were male, with a median age of 56 years (44–74). Tumor localization was choroidal in 9 patients and ciliary body in 3 patients. Tumor stage distribution was as follows: 2 patients in stage I, 6 in stage IIA, 1 in stage IIB, and 3 in stage IIIB. The median tumor diameter and thickness were 12 mm (5.5–15) and 6 mm (1.8–15), respectively. Except for one patient who underwent surgery after preoperative SRT, all patients were treated with curative intent. Median PTV volume was 1.02 cm³ (0.15–6.35). Median total dose was 46.5 Gy (21–54) delivered in 3 fractions (1–3); median BED10 was 118.65 Gy (35.7–151.2). Median treatment time was 17.5 minutes (12–24) (detailed in Table 1). Median logarithm of the minimum angle of resolution (logMAR) before treatment, at 6 months, at 12 months, and at the last follow-up was 0.35 (0.05–2.7), 1.55 (0.1–2.7), 2.3 (0.15–3), and 2 (0.05–3), respectively; visual acuity improved in 3 patients, remained stable in 2, and worsened in 7. At the 6 month tumor response evaluation, partial response was achieved in 6 patients, while 6 patients showed stable disease. During treatment, grade 1 periorbital edema was observed in 1 patient and grade 2 epiphora in 2 patients. Late toxicity occurred 8 events in 7 patients (58.3%): retinal detachment in 4 (2 grade 4, 2 grade 3), vitreous hemorrhage in 3 (2 grade 4, 1 grade 2), and radiation retinopathy in 1 (grade 2). No optic neuropathy was observed. A strong positive correlation was found between PTV volume and the retinal 2 Gy equivalent dose (retinaEQD2) Dmean parameter (r = 0.776, p = 0.003). However, retinaEQD2 D0.03cm³, Dmean, D0.2cm³ doses, and PTV volume did not differ statistically significantly according to the development of retinal toxicity. During the median follow-up period, no local recurrence was observed, and the local relapse-free survival rate was 100%. However, metastases developed in 2 patients, and 1 of these patients died. CONCLUSION CK-M6–based SRT achieved 100% local control at a median follow-up of 22 months in UM. However, severe adverse events (grade >=3) occurred in 6 patients (50%), and most patients did not experience visual improvement. Toxicity may be related to limited sample size, larger PTV volumes, tumor location, and proximity to the fovea. While CK-M6 SRT is effective and non-invasive with short treatment time, toxicity requires careful attention.