Visual Outcome and Millimeter Incremental Risk of Metastasis in 1780 Patients With Small Choroidal Melanoma Managed by Plaque Radiotherapy

IMPORTANCE Early detection of choroidal melanoma at a small tumor size is emphasized in the literature. However, there is little published information on the specific risks of plaque-irradiated small choroidal melanoma on visual acuity and metastasis. OBJECTIVE To analyze outcomes of plaque radiotherapy for small choroidal melanoma 3 mm in thickness or less. DESIGN, SETTING, AND PARTICIPANTS This retrospective noncomparative series at a tertiary referral center included 1780 consecutive patients who had received plaque radiotherapy treatment for small choroidal melanoma. MAIN OUTCOMES AND MEASURES Visual acuity outcomes and melanoma-associated metastasis, assessed by Kaplan-Meier analyses. RESULTS The mean (SD) patient age at melanoma diagnosis was 58 (14) years. Of 1780 patients, 908 were female (51.0%), and 1752 were white (98.4%). Visual acuity was 20/40 OU or better in 1276 of the patients (71.7%), and the mean (SD) visual acuity was 20/40 (20/50) OU (median, 20/30; range, 20/20 to counting fingers). The mean (SD) tumor basal dimension was 8.8 (2.9) mm(median, 8.0 mm; range, 2.0-20.0 mm) and mean (SD) tumor thickness was 2.6 (0.5) mm(median, 2.7; range, 0.2-3.4 mm). Mean (SD) distance to the foveola was 3.4 (3.9) mm and to the optic disc was 3.7 (3.7) mm. The Kaplan-Meier rate of visual acuity loss (>= 3 Snellen lines) was 9.5%(95% CI, 8.2%-11.0%) at 1 year, 39.2%(95% CI, 36.5%-42.0%) at 5 years, and 48.9%(95% CI, 45.6%-52.3%) at 10 years, whereas poor visual acuity (>= 20/200) was 7.1%(95% CI, 5.9%-8.4%) at 1 year, 38.2%(95% CI, 35.5%-41.1%) at 5 years, and 53.5%(95% CI, 50.1%-57.1%) at 10 years. Regarding melanoma-associated metastasis, the rate was 0.2%(95% CI, 0.09%-0.6%) at 1 year, 4.5% (95% CI, 3.4%-5.9%) at 5 years, and 8.8% (95% CI, 6.9%-11.1%) at 10 years. Using 1.0-mm thickness increments, the 10-year risk formetastasis was 25.0% (95% CI, 3.9%-87.2%) at 0-mm to 1.0-mm thickness, 5.9% (95% CI, 2.5%-13.5%) at 1.1-mm to 2.0-mm thickness, 8.1% (95% CI, 5.9%-11.0%) at 2.1-mm to 3.0-mm thickness, and 13.4%(95% CI, 8.7%-20.4%) at thicknesses greater than 3.0 mm. The greater relative risk (RR) formetastasis in thinnest tumors was 1.83 (95% CI, 1.09-3.07), which likely represented more aggressive diffuse (flat) melanoma. By multivariable analysis, clinical features predictive of melanoma-associated metastasis included increasing patient age (RR, 1.32 [95% CI, 1.07-1.63] per decade; P = .01), tumor diameter (RR, 1.15 [95% CI, 1.06-1.24] per mm; P < .001), tumor thickness (RR, 2.22 [95% CI, 1.22-4.05] per mm; P = .01), photopsia symptoms (RR, 2.45 [95% CI, 1.35-4.43]; P = .003), and prior treatment before plaque radiotherapy (RR, 3.31 [95% CI, 1.31-8.33]; P = .01). CONCLUSIONS AND RELEVANCE This retrospective study suggests that small choroidal melanoma treated with plaque radiotherapy has a 10-year risk for visual acuity loss of 48.9% (95% CI, 45.6%-52.3%) and a 10-risk of systemic metastasis of 8.8% (95% CI, 6.9%-11.1%). In this analysis, each millimeter of increasing thickness and diameter contributed risk for metastatic disease.