A novel radiosurgical platform to treat a case of uveal melanoma

(Image credit: Georgii/AdobeStock)

A relatively new technology, The ZAP-X system (Zap Surgical Systems Inc., San Carlos, CA), described by investigators as a “dedicated self-contained and self-shielded surgical robot for performing stereotactic surgery (SRS) of the brain, head, and neck,” was used to treat a patient with uveal melanoma.

The investigative team, led by Stephan Kinzl, MD, explained that “SRS is a recognized procedure for treating benign tumors including vestibular schwannoma, meningioma, pituitary adenoma, neuroma of other cranial nerves, and glomus-jugular tumors, and malignant tumors like brain metastasis, glioblastoma recurrence, and chondrosarcoma and for treating trigeminal neuralgia and arteriovenous malformations. Dr. Kinzl is from the Department of Ophthalmology, Stadtspital Zurich, Zurich. He and his colleagues reported their experience with the Zap-X system in Cureus.¹

Uveal melanoma, which primarily affects Caucasian patients, is the most common primary intraocular tumor in adults² that most often affects the choroid (90%), ciliary body (6%), and iris (4%).³ 

A number of different options are available for treating uveal melanoma, ie, transpupillary thermotherapy; photodynamic therapy; radiotherapy (plaque radiotherapy, proton beam radiotherapy, Gamma Knife radiosurgery [Elekta, Stockholm, Sweden], CyberKnife radiosurgery [Accuray, Madison, WI], and linear accelerator [LINAC)-based radiosurgery]; and resection, enucleation, and exenteration²; and SRS.

SRS has become a well-established treatment for uveal melanoma. It has the advantage of a single-session delivery treatment without requiring invasive surgery for plaque implantation or prolonged hospitalization,⁴ the authors explained.

The results achieved with SRS are similar to those achieved with other radiotherapy techniques. The survival rates are similar to those of brachytherapy, proton beam irradiation, or enucleation.^5-7

However, the investigators pointed out, the 5-year mortality rate for patients with uveal melanoma has not changed in the past 30 years.⁸ Only the cancer immunotherapy, tebentafusp (Kimmtrak, Immunocore Holdings), approved in 2022, can extend the life expectancy of patients in whom the uveal melanoma has metastasized.⁹

Case report

The investigators reported one of the first cases of uveal melanoma treated with SRS using the ZAP-X platform.

A 78-year-old woman presented with the complaint of reduced vision vision in her right eye for about 3 to 6 weeks. The visual acuity was hand motions in the affected eye and 20/25 in the left eye. The intraocular pressures, bilateral anterior segment examinations, and fundus examination of the left eye were unremarkable. Her ophthalmic and past medical histories also were unremarkable.

Evaluation showed a collar-button uveal melanoma in the right eye with a 9.90-mm largest basal diameter and a 12.97-mm ultrasonographic thickness with associated neurosensory detachment. The gross tumor volume (GTV) was 1.47 cm3 and was defined geometrically and stereotactically in three dimensions using imaging data. The planning target volume (PTV) was created by adding a 2-mm isotropic margin around the GTV to account for setup and patient uncertainties, the authors explained.

The tumor was considered to be a large uveal melanoma based on The Collaborative Ocular Melanoma Study classification.¹⁰ Radiotherapy as a globe-sparing technique was the therapy of choice. Reported tumor control rates after SRS are 84% to 100%, with eye preservation in 78% to 97.4% of cases.¹¹ The justification for using the high-precision ZAP-X delivery system to treat this patient was the ability to offer the patient a therapy without the need for retrobulbar anesthesia and surgical intervention in an outpatient setting.

Th authors administered the maximal dose of 33.3 Gy in the center and applied the prescription dose of 18 Gy to the 54% isodose around the PTV. Akinesia of the ocular globe was achieved by mechanical vacuum fixation, and the pupillary center deviation was assessed continuously during treatment using an infrared camera to stop dose delivery instantly in the event of abnormal bulbus movement. The treatment was delivered in one session. The authors reported that at the 6- and 12-month follow-up evaluations the volume of the melanoma decreased. No major complications were recorded.

“This case report demonstrates the successful use of the ZAP-X stereotactic radiotherapy system for the efficient and effective treatment of a uveal melanoma with a notable reduction in tumor size at the 6- and 12-month follow-up visits without any serious adverse effects. It is yet to be confirmed whether these results can be replicated in a larger patient cohort,” the authors concluded.

References

1. Kinzl S, Heussen F, Kaiser K, et al.Treatment of uveal melanoma using a novel radiosurgical platform: a case report. Cureus. 2025;17: e81343.doi:10.7759/cureus.81343

2. Kaliki S, Shields CL. Uveal melanoma: relatively rare but deadly cancer. Eye (Lond).2017;31:241-257.10.1038/eye.2016.275

3. Shields CL, Kaliki S, Furuta M, Fulco E, Alarcon C, Shields JA. American Joint Committee on Cancer classification of posterior uveal melanoma (tumor size category) predicts prognosis in 7731 patients. Ophthalmology.2013;120:2066-2071. 10.1016/j.ophtha.2013.03.012

4. Liegl R, Schmelter V, Fuerweger C, et al. Robotic CyberKnife radiosurgery for the treatment of choroidal and ciliary body melanoma. Am J Ophthalmol.2023;250:177-185. 10.1016/j.ajo.2022.12.021

5. Branisteanu DC, Bogdanici CM, Branisteanu DE, et al.Uveal melanoma diagnosis and current treatment options (Review). Exp Ther Med.2021;22:1428.10.3892/etm.2021.10863

6. Seddon JM, Gragoudas ES, Albert DM, Cheng Hsieh C, Polivogianis L, Friedenberg GR. Comparison of survival rates for patients with uveal melanoma after treatment with proton beam irradiation or enucleation. Am J Ophthalmol.1985;99:282-290.10.1016/0002-9394(85)90357-5

7. Dunavoelgyi R, Dieckmann K, Gleiss A, et al.Local tumor control, visual acuity, and survival after hypofractionated stereotactic photon radiotherapy of choroidal melanoma in 212 patients treated between 1997 and 2007. Int J Radiat Oncol Biol Phys.2011;81:199-205.10.1016/j.ijrobp.2010.04.035

8. Stålhammar G, Herrspiegel C. Long-term relative survival in uveal melanoma: a systematic review and meta-analysis. Commun Med (Lond).2022;2:18.10.1038/s43856-022-00082-y

9. Nathan P, Hassel JC, Rutkowski P, et al.Overall survival benefit with tebentafusp in metastatic uveal melanoma. N Engl J Med. 2021;385:1196-1206.10.1056/NEJMoa2103485

10. Margo CE. The Collaborative Ocular Melanoma Study: an overview. Cancer Control. 2004, 11:304-309. 10.1177/107327480401100504

11. Suesskind D, Scheiderbauer J, Buchgeister M, et al.Retrospective evaluation of patients with uveal melanoma treated by stereotactic radiosurgery with and without tumor resection. JAMA Ophthalmol. 2013, 131:630-637.10.1001/jamaophthalmol.2013.697