Medical Retina : Case five

This 47 year old man was referred to London for treatment of a suspected choroidal melanoma in the left eye. This is the appearance of his left eye three months later.

a. What treatment did he receive?

Plaque radiotherapy.
The picture shows a pigmented lesion (the choroidal melanoma) superotemporal to the optic disc with extensive hard exude. The exude is caused by the breakdown of blood retina barrier due to radiation retinopathy.

Plaque radiotherapy is the most common form of conservative treatment for choroidal melanoma. The plaque is sutured to the sclera directly over the tumour. The implant is usually left in place for 5 to 7 days until the desired dose has been delivered. This conventionally about 70 - 100 Gy at the tumour apex. Ruthenium plaque and iodine plaque are the most commonly used.
 

b. Which types of choroidal melanoma are suitable for such treatment?

Plaque radiotherapy is used to preserve the globe and is the treatment of choice in small and medium size tumour. Large tumour and those with retinal detachment are not suitable.

The thickness of the tumour will determine on the type of plaque used. Ruthenium plaque emits beta radiation and is suitable for tumour less than 5 mm in thickness. Iodine plaque emits gamma radiation and is suitable for tumour up to 8 mm in thickness.

c. What complication can occur with this form of treatment?

Complications include:

• loss of visual acuity due to radiation maculopathy resulting  from the break-down of blood retina barrier
• radiation retinopathy with ischaemia and neovascularization
• optic neuropathy
• neovascular glaucoma
• uveitis
• cataract

d. What factors are of prognostic importance in choroidal melanoma?

The main factors of prognostic importance are:

• cell type. Epithelioid cells have poorer prognosis than spindle cell types
• tumour size. Larger tumour has poorer prognosis
• extrascleral spread
• age of the patient. Older patients tend to have poorer prognosis