Shields CL, et al. - Authors evaluated the outcomes of plaque radiotherapy for small choroidal melanoma 3 mm in thickness or less. A 10-year risk for visual acuity loss of 48.9% and a 10-risk of systemic metastasis of 8.8% was seen in small choroidal melanoma treated with plaque radiotherapy. They noted a contribution of each millimeter of increasing thickness and diameter to the metastatic disease risk.

Methods

• In this retrospective noncomparative series at a tertiary referral center, experts included 1,780 consecutive patients who had received plaque radiotherapy treatment for small choroidal melanoma.
• Main outcomes and measures were visual acuity outcomes and melanoma-associated metastasis, as assessed by Kaplan-Meier analyses.

Results

• As per data, the mean (SD) patient age at melanoma diagnosis was 58 (14) years; out of 1,780 patients, 908 were female (51.0%), and 1,752 were white (98.4%).
• In 1,276 of the patients (71.7%), visual acuity was 20/40 OU or better, and the mean (SD) visual acuity was 20/40 (20/50) OU (median, 20/30; range, 20/20 to counting fingers).
• Results demonstrated that 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); 3.4 (3.9) mm was the mean (SD) distance to the foveola and to the optic disc it was 3.7 (3.7) mm.
• At 1 year, the Kaplan-Meier rate of visual acuity loss (≥3 Snellen lines) was 9.5% (95% CI, 8.2%-11.0%), it was 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.
• The rate for melanoma-associated metastasis 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 for metastasis 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) for metastasis in thinnest tumors was 1.83 (95% CI, 1.09-3.07), which likely represented more aggressive diffuse (flat) melanoma.
• By multivariable analysis, 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) were included in clinical features predictive of melanoma-associated metastasis.