Vitrectomy with brachytherapy shows no increase in metastatic risk

There is controversy surrounding whether to perform intraocular surgery in eyes with uveal melanoma because of concerns about orbital dissemination and fear of a possible increase in the metastatic risk.

The results of a recent study should put those fears to rest in that the chief finding was that vitrectomy performed at the time of brachytherapy does not increase patients’ metastatic prognosis.

Tara McCannel, MD, PhD, and colleagues have identified a number of benefits associated with the use of silicone oil. In previous studies, they established that silicone oil of 1,000 cSt can attenuate radiation during brachytherapy by from 50% to 60%, reduce radiation retinopathy by 2 years, delay the severity of progression of angiographic radiation retinopathy, and significantly improve vision in patients with a large choroidal melanoma compared to plaque therapy alone at 2 years.

Dr. McCannel, director of the Ophthalmic Oncology Center, Jules Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles (UCLA), explained how silicone oil works in preventing radiation retinopathy.

“When treating melanoma, we place a plaque on the sclera,” Dr. McCannel explained. “To actively treat the lesion, some of the radiation affects the other healthy tissues in the eye. If we can replace the vitreous with a substitute that contains the iodine-125 radiation, such as silicone oil, then the radiation effect on the healthy tissues can be minimized.”

Retrospective study

She and her colleagues conducted a retrospective study at UCLA in which they investigated the mortality rate associated with metastasis from choroidal melanoma among patients treated with vitrectomy and placement of silicone oil to prevent retinopathy during iodine-125 brachytherapy.

All patients were treated from February 2010 to July 2016 and were followed for 1 year after surgery. During the study, the investigators evaluated the tumor characteristics, metastatic death, and molecular prognostic markers in metastatic cases.

In phakic cases, clear cornea phacoemulsification was performed with implantation of an intraocular lens (IOL); standard plaque therapy alone then was performed followed by a 23-gauge complete vitrectomy, detachment of the posterior hyaloid membrane, peripheral shave, air-fluid exchange, injection of silicone oil (1,000 cSt), and suturing of the sclerotomies.

Study results

A total of 283 cases were included. The mean follow-up time was 34.1 months (range, 1-7 years). The average tumor height was 4.8 mm ± 2.9 mm and the greatest basal dimension was 12.0 mm ± 3.2 mm.

Two surgeries were performed: the first, vitrectomy, injection of silicon oil, and placement of a plaque in 102 patients (36.4%). The second included phacoemulsification, IOL implantation, vitrectomy, injection of silicone oil, and placement of a plaque in 180 patients (63.6%).

Of these, 20 patients (7.1%) died as a result of metastasis. The Kaplan-Meier 5-year cumulative mortality estimate was 14.2% (95% confidence interval, 7.7%-25.5%), Dr. McCannel reported.

Metastatic risk

Another question that the investigators looked at was whether performing more surgery increased the metastatic risk. “Metastasis developed in 8 patients [40%] in the vitrectomy/silicone oil group and in 12 patients [60%] in the phacoemulsification/vitrectomy group,” Dr. McCannel said. “The individualized Kaplan-Meier survival estimates in the 2 groups showed no significant difference (88.4% versus 88.2%, respectively).”

When the investigators evaluated the biopsies from those patients in whom metastasis developed, 19 patients underwent fluorescence in situ hybridization for chromosomes 3 and 6 and most had monosomy 3. Gene expression profile results in 13 of the 19 patients showed that most patients were in class 2, she pointed out.

The investigators also compared the Kaplan-Meier survival estimates with that of the Collaborative Ocular Melanoma Study (COMS). “The comparison showed there was no difference in the 5-year cumulative mortality estimate compared to the COMS patients who were treated with plaque alone and those in the current cohort treated with vitrectomy and silicone oil and 60% of those underwent phacoemulsification, IOL implantation, and silicone oil placement,” Dr. McCannel said.

The study results indicated that vitrectomy with silicone oil placement resulted in no significant difference in the 3- and 5-year survival rates compared to the COMS data.

“More surgery did not result in greater mortality,” Dr. McCannel outlined. “Metastatic death was associated with the molecular biology of the tumor, specifically monsomy 3 or class 2, and not additional intraocular procedures. Finally, vitrectomy with silicone oil radiation attenuation is a vision-improving strategy without evidence of increased systemic risk.”

Tara A. McCannel, MD, PhD

e. tmccannel@jsei.ucla.edu

This article was adapted from a presentation Dr. McCannel delivered at the 2017 American Society of Retina Specialists. Dr. McCannel is a consultant and advisor to Impact Genetics and Novartis Pharmaceuticals.