Treatment of uveal melanoma
Why are uveal melanomas treated?
The objectives of treatment are to:
- prevent metastatic spread, if this has not already happened.
- conserve the eye with as much useful vision as possible.
- avoid pain and disfigurement.
How are uveal melanomas treated?
The treatment of uveal melanomas varies greatly between centres. There are many reasons for this:
- Ocular oncologists have different views about the indications and contraindications of each kind of therapy.
- Most have only one or two types of treatment at their disposal so that their choice is limited. This may be because they are seeing small numbers of patients with ocular melanoma or practicing ocular oncology only part time.
- Many are constrained by the methods they have inherited from their predecessors in their departments.
Factors considered when selecting treatment for an individual patient:
- basal tumor diameter.
- tumor thickness.
- proximity of tumor to optic nerve and fovea.
- extent of involvement of ciliary body, iris and angle.
- whether or not the tumor has perforated retina.
- whether the tumor has extended through sclera and if so how big the tumor is outside the eye.
- the harm caused to the eye by the tumor (i.e., the 'secondary effects') (e.g., retinal detachment, neovascular glaucoma).
- the visual acuity in the fellow eye.
- the visual demands of the patient (e.g., as determined by occupation).
- the patient's general health and life expectancy.
- the patient's wishes, needs and fears.
- the patient's attitude to risks such as local tumor recurrence, ocular complications and loss of the eye.
- how the patient feels about traveling several times to the hospital for treatment and long-term surveillance.
The various treatments include:
- proton beam radiotherapy
- plaque radiotherapy (i.e., 'brachytherapy')
- stereotactic radiotherapy
- trans-scleral local choroidectomy (also called 'exoresection')
- trans-scleral cyclectomy (also known as 'iridocyclectomy')
- trans-scleral iridectomy (also known as 'iridectomy')
- trans-retinal local resection (also called 'endoresection')
- transpupillary thermotherapy
- photodynamic therapy
In many centers, the first choice of treatment is radiotherapy, which can consist of plaque radiotherapy, proton beam radiotherapy or stereotactic radiotherapy. Each method has its advantages and disadvantages.
Our first choice of treatment at UCSF is proton beam radiotherapy. This requires a surgical procedure for insertion of tantalum markers behind the eye so that the proton beam can be aimed accurately at the tumor.
At present, we perform eyewall resection only for small tumors near the front of the eye, in the ciliary body. This procedure is called iridocyclectomy.
Trans-scleral local resection of choroidal tumors requires profound lowering of the blood pressure, to prevent excessive bleeding, and few anesthesiologists are prepared to do this, because of the risks involved (i.e., stroke, heart attack and sudden death).
We avoid iridectomy for iris melanomas, which we prefer to treat with proton beam radiotherapy, without marker insertion.
We do not need to use stereotactic radiotherapy, because we are fortunate that proton beam radiotherapy is available to us.
With tumors touching the nerve, radiotherapy almost always causes severe optic nerve damage and loss of all useful vision. For this reason, some patients are treated by endoresection. This is a controversial operation because of fears that cutting into the tumor might scatter cancerous cells around the eye and to other parts of the body. Experience with more than a hundred such operations suggests that fears about uveal melanoma dissemination are exaggerated. In any case, we recommend endoresection only if offers the best hope for conserving useful vision and if the patient accepts the controversial nature of the operation. This is combined with laser treatment and, sometimes, a low dose of radiotherapy to reduce the risk of local tumor recurrence.
Transpupillary thermotherapy and photodynamic therapy are not as reliable as radiotherapy and so we reserve such phototherapy for very small tumours and in patients who accept the increased risk of local tumor recurrence and hence the need for radiotherapy at a later stage.
We resort to enucleation only if the chances of conserving the eye and useful vision are small or if the patient is not sufficiently motivated to undergo radiotherapy or local resection.
Ciliary body melanomas
If the ciliary body melanoma is small, our first choice of treatment is cyclectomy, because this is usually a quick and straightforward operation (for experienced surgeons) with good results. Furthermore, this treatment provides tumor tissue for diagnosis and for prognostic laboratory studies (i.e., predicting future health). If the tumor involves the iris, then part of this tissue may need to be removed (i.e., iridocyclectomy) whereas if the tumor extends back into choroid then 'choroido-cyclectomy' would be required, but as this surgery is more difficult and risky we would prefer some form of radiotherapy.
If there is extensive ciliary body involvement by the tumor, that is, exceeding two clock hours, then we would prefer proton beam radiotherapy. This is because of the risk of ocular hyopotony (i.e., low intraocular pressure) and phthisis (i.e., shrinkage of the eye) if too much of the ciliary body is removed (because it is the ciliary body that pumps water into the eye to maintain pressure).
If the tumour is very extensive, then enucleation (i.e., ocular removal) may be the best option. Most patients having this operation are pleasantly surprised afterwards, because the reality of living with an artificial eye is much better than they expected.
Our preferred treatment for iris melanoma is proton beam radiotherapy. Unlike surgical excision (i.e., 'iridectomy'), radiotherapy does not cause a very large and irregular pupil, or a distorted pupil if suturing is attempted (i.e., 'pupilloplasty'). Proton beam radiotherapy can successfully treat iris tumours that are too extensive for surgical excision.
Unlike iridectomy and plaque radiotherapy, proton beam treatment is a no-touch technique and does not require inpatient care.
Enucleation may be necessary if the iris melanoma is very advanced.
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