A randomized controlled trial of varying radiation doses in the treatment of choroidal melanoma

Objective: To determine if a reduction in proton radiation dose from the st andard dose of 70 cobalt gray equivalents (CGE) to 50 CGE would decrease ra diation-induced complications, thereby improving visual prognosis, without compromising local tumor control for patients with uveal melanoma at high r isk of these complications. Design: Randomized, double-masked clinical trial. Participants: A total of 188 patients with small or medium-sized choroidal melanomas (<15 mm in diameter and <5 mm in height) near the optic disc or m acula (within 4 disc diameters of either structure). Methods: Patients were treated with proton beam therapy at doses of either 50 CGE or 70 CGE between October 1989 and July 1994, and followed up biannu ally through April 1998. Outcomes included visual acuity, radiation complic ations, melanoma recurrence, and metastasis. Results: Proportions of patients retaining visual acuity of at least 20/200 were similar in the 2 dose groups at 5 years after radiation (approximatel y 55%). Similar numbers of patients in each group experienced tumor regrowt h (2 patients at 50 CGE vs 3 patients at 70 CGE; P > .99) and metastasis (7 patients at 50 CGE vs 8 patients at 70 CGE; P = .79). Five-year rates of r adiation maculopathy also were similar (for both groups, approximately 75% for tumors within 1 disc diameter and 40% for tumors > 1 disc diameter from the macula). Rates of radiation papillopathy were nonsignificantly decreas ed in the 50-CGE treatment group when tumors were located 1 disc diameter o r less from the optic disc (P = .20). Patients treated with the lower dose also experienced significantly less visual field loss. Conclusions: This level of dose reduction did not result in a lesser degree of visual acuity loss. The lower-dose group did experience significantly l ess visual field loss. Local tumor recurrence and metastatic death rates we re similar in both dose groups.