In uveal melanoma, the COMS (Collaborative Ocular Melanoma Study) showed that compared to enucleation, pre-enucleation radiotherapy for large tumours:

• A Significantly improved 5-year survival by reducing micrometastasis
• B Resulted in worse local control due to radiation-induced vasodilation
• C Was beneficial only for choroidal melanomas, not ciliary body tumours
• D Did not improve survival; the 5-year mortality was similar regardless of treatment ✓

Explanation

The COMS for large choroidal melanomas randomised patients to pre-enucleation radiotherapy (20 Gy) plus enucleation versus enucleation alone. At 5 years and 10 years, the mortality rates were virtually identical (~25% at 5 years), disproving the hypothesis that pre-enucleation radiation prevents haematogenous dissemination of tumour cells. This is because uveal melanoma metastasises haematogenously (primarily to liver) early and micrometastases are present at diagnosis in patients who die of disease. Proton beam and brachytherapy (iodine-125 plaque, COMS medium tumour study) are now preferred for medium tumours as globe-conserving alternatives.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.