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.
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Contributors MF performed the data conception, helped in collecting data, analysis of data, drafting the article and revising the article. ET helped in drafting and revising the article. CH helped in revising the article. SS performed the data conception and helped in revising the article. GS helped in data conception, drafting the article, data analysis and interpretation and revising the article. All authors read and approved the final manuscript.
Funding Funding/support for this study was provided to Gustav Stålhammar by Karolinska Institutet (Karolinska Institutets stiftelsemedel för ögonforskning) and by Stockholm County Council (Stockholms läns landsting).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Regional ethical review board in Stockholm, Sweden.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon resonable request to the corresponding author.
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