Approximately half of all patients with posterior uveal melanoma develop metastatic liver disease within 15 years. Although brachytherapy utilizing current isotopes may be hindered by associated toxicities, the isotope ruthenium-106 has been reintroduced into the U.S. market. In a study published in Practical Radiation Oncology, Takiar et al revisited the safety and efficacy of ruthenium-106–based brachytherapy in patients with uveal melanoma and found excellent tumor control and acceptable toxicity.
Uveal tract melanomas represent about 3% of all melanoma diagnosed in the United States and are generally seen in older and mostly male patients. Approximately half of all patients with posterior uveal melanoma develop metastatic liver disease within 15 years of diagnosis.
Although enucleation remained the standard of care into the 1970s, this treatment approach appeared to contribute to an increased risk of metastatic dissemination. Thus, alternative treatment modalities were explored, including radiation (both brachytherapy and teletherapy). Although brachytherapy was found to provide ocular preservation, it was associated with toxicity.
Newer isotopes have been identified to minimize associated toxicities, including palladium-103, strontium-90, and ruthenium-106. Ruthenium-106, a beta-emitter with a relatively limited depth of dose penetration, was only recently reintroduced to the U.S. market after being removed in 2007.
The investigators retrospectively analyzed the medical records of 40 patients with uveal melanoma who were treated with brachytherapy using ruthenium-106 in commercially available plaques. Based on the dimensions of the lesion and proximity to the optic nerve, the appropriate plaque size and shape were chosen.
Patients were scheduled at 3- to 6-month intervals for follow-up, or sooner if they were symptomatic. At the time of follow-up, each patient was seen by the treating ophthalmologist, who performed a complete history and ophthalmologic examination.
Patients were subdivided into groups based on preimplant and postimplant visual acuity in the affected eye for detailed analysis, with movement between groups characterized as clinically significant visual loss. Implant duration ranged from 30.8 to 219.7 hours, with a median of 88.9 hours; this duration was based on the activity of the isotope and required prescription depth.
Among the 40 patients, 1 patient had melanoma of the ciliary body, 25 patients had melanoma of the choroid, and 14 patients were identified globally as having uveal melanoma. There were 20 females and 20 males. The median age at the time of brachytherapy implant was 59 years (range, 37–82 years).
At 2 years, the overall survival rate was 97%, and at 5 years, it was 92%. Three deaths occurred; two were associated with disease progression and one was due to myocardial infarction. Fifteen patients experienced clinically significant visual loss, whereas the remaining 25 patients had equal or improved visual acuity.
Twenty patients were diagnosed with cataracts following implant in the treated eye; of these, only one patient was deemed to have a clinically significant radiation-induced cataract. None of the patients was diagnosed with neovascular glaucoma that was attributable to brachytherapy. One patient was reported to have optic neuropathy, and two patients had radiation-induced vitreous hemorrhage.
The investigators affirmed that brachytherapy utilizing ruthenium-106 was safe and effective in patients with uveal melanoma. They indicated that none of the patients in their study experienced enucleations. This was a reflection of the fact that no patient from their study population experienced local relapse alone.
As for radiation-related toxicities, the cataract rate of 50% was deemed to be low, considering the older age of patients at the time of implant. In addition, with regard to visual acuity, 62.5% of patients maintained their preimplant visual acuity. According to the investigators, these data support the reintroduction of ruthenium-106 into clinical practice for ocular melanoma.
“Our findings corroborate previously published reports from other countries that demonstrate the efficacy of treating medium-sized ocular melanomas with brachytherapy using ruthenium-106 plaques, particularly those less than 5 mm in apical height,” concluded the investigators.
Beth M. Beadle, MD PhD, of The University of Texas MD Anderson Cancer Center, is the corresponding author of the article in Practical Radiation Oncology.
The authors reported no conflicts of interest.
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