Effect of plaque brachytherapy dose and dose rate on risk for disease-related mortality in 1238 patients with choroidal melanoma.

ABSTRACT

BACKGROUND: Episcleral brachytherapy is the most common treatment for medium-sized choroidal melanomas. Although controversial, inadequate brachytherapy dose and dose rates have at least a hypothetical implication on patient survival. METHODS: All patients who received ruthenium-106 or iodine-125 brachytherapy for choroidal melanoma at St. Erik Eye Hospital 1996 to 2016 were included (n=1238). Cox regression hazard ratios for melanoma-related mortality across deciles, quartiles and individual integers of apex radiation doses (Gy) and dose rates (Gy/hour) were calculated, adjusted for tumour size and location. RESULTS: The average radiation dose at the tumour apex ranged from 73.0 Gy in the first decile to 108.6 Gy in the tenth. Decreasing apex dose by 1 Gy increments or by decile or quartile group was not associated with melanoma-related mortality (p>0.2) The average radiation dose rate at the tumour apex ranged from 0.5 Gy/hour in the first decile to 2.8 Gy/hour in the tenth. Similarly, decreasing apex dose rate by 1 Gy/hour increments or by decile or quartile groups was not associated with melanoma-related mortality (p>0.5). CONCLUSION: There are no increased hazards for choroidal melanoma-related mortality after brachytherapy with decreasing doses between 108.6 and 73.0 Gy, or with decreasing dose rates between 2.8 and 0.5 Gy/hour.