PROTON BEAM THERAPY FOR CHOROIDAL MELANOMAS

Proton beam irradiation of large choroidal melanomas provides good eye retention and tumor control out to 10 years, according to a retrospective study.

"Proton beam irradiation is a very good option for first-line therapy in patients with large choroidal melanomas who wish to keep their eye and have some hope of retaining ambulatory vision in the affected eye,” Dr. Ivana K. Kim from Massachusetts Eye and Ear, Harvard Medical School, in Boston, told Reuters Health by email. “Many large tumors that aren’t amenable to treatment with plaque brachytherapy can be effectively treated with protons.”

Radiotherapy has emerged as an effective alternative to enucleation for treating large melanomas, and proton beam irradiation (PBI), in particular, can spare sensitive structures of the eye while delivering an effective dose of radiation to the tumor.

Dr. Kim's team analyzed long-term outcomes after PBI among 336 patients with large choroidal melanomas (median dimensions, 18.0 mm basal diameter and 8.7 mm height). More than a third of patients (39.0%) had at least 10 years of follow-up.

Findings were published online October 19 in JAMA Ophthalmology.

Most patients (76.2%) had retinal detachment at baseline, 61.0% had tumors within two disc diameters of the optic nerve, and 32.4% of patients had optic nerve involvement and tumors >8 mm.

Baseline visual acuity was at least 20/40 in 39.0% of patients, at least 20/200 in 72.6% of patients, and worse than 20/800 in 15.5% of patients.

Visual acuity diminished considerably beyond 1 year after treatment, and only 8.7% of patients retained acuity of 20/200 or better at 10 years. Results were better for patients whose tumors were located more than two disc diameters from the optic nerve and fovea (20.1% with 20/200 acuity at 10 years).

At 10 years, 70.4% of patients retained their eyes, with higher eye conservation rates among those with tumors located farther away from critical structures (82.7%).

Neo-vascular glaucoma was common: at 10 years, 44.8% of patients with tumors located within two disc diameters of the optic nerve and/or fovea and 36.2% of those with tumors farther away.

Tumors recurred locally in 12.5% of patients at 10 years, and melanoma-related mortality was 48.5% by 10 years after PBI.

“The rates of metastasis are similar between proton therapy and enucleation, and while rates of radiation-related ocular complications are significant, there is still hope for retention of vision and retention of the eye over the long-term,” Dr. Kim said.

“Rates of local recurrence continue to increase between 5 and 10 years,” she added. “Therefore, these patients need regular ophthalmic follow-up for the very long-term.”

Dr. Tom Pickles from British Columbia Cancer Agency and the University of British Columbia, in Canada, who recently reported similar outcomes there, told Reuters Health by email, "Conservative measures, such as proton therapy and plaque brachytherapy, are alternatives that should be considered, rather than enucleation (which still has an important role with very large tumors, etc.).”

“All patients with uveal melanoma should be assessed in a multidisciplinary clinic, preferably at a center where the full range of treatment options are available, i.e., brachytherapy plaque, proton therapy, observation, enucleation, etc. Proton therapy definitely has a role, which this paper illustrates well.”

Dr. Sung Ho Moon from National Cancer Center, Goyang, Korea, told Reuters Health by email, "The incidence rate of choroidal melanoma in Asian population is much lower, compared with in whites. So, most ophthalmologists in our country have some skepticism about radiation therapy, including PBI and plaque therapy, for large choroidal melanoma. Actually, they usually recommend enucleation as the first treatment option for these patients.”

“During the past 8-9 years of applying PBI to patients with choroidal melanoma, I have felt that they had a considerable fear, which is beyond the expectation of healthy people, when they heard that their eye should be removed,” he said. “Nearly all patients I met were satisfied and accepted the vision decrease or loss, because they maintained their treated eye and many people around them did not notice they had a serious ocular illness.”

“At this point, PBI should have a position of the first treatment option for patients with large choroidal melanoma because another eyeball-sparing option, plaque therapy, has some limitation in this population” Dr. Moon concluded. “Vision sparing, I think, is a secondary concern for patients with large choroidal melanoma as long as the untreated eye is useful.”