Melanoma/Skin Cancer Health Center

The natural history of small choroidal melanoma remains poorly understood. Small, pigmented choroidal lesions cannot always be differentiated reliably on examination. Growth is a presumed indicator of malignant potential.[1]

Although patients diagnosed with small choroidal tumors were not eligible for participation in the Collaborative Ocular Melanoma Study, these patients were offered participation in a prospective follow-up study to evaluate the natural history of small lesions. Two-year and 5-year tumor growth estimates of 21% and 31%, respectively, were reported.[2] Clinical risk factors associated with tumor growth included increased tumor thickness, presence of subretinal fluid, orange pigmentation, absence of drusen, absence of retinal pigment, margin at the optic disc, and epithelial changes surrounding the tumor.[2,3]

The 5-year melanoma-related mortality rate in patients treated for small choroidal melanomas has been reported as high as 12%.[4,5] Several studies indicate that the two most important clinical factors predictive of mortality are larger tumor size (at the time of treatment) and documentation of tumor growth.[6]

Typical features of the tumor on ophthalmoscopy, fluorescein angiography, and ultrasound examination of the eye contribute to the clinical diagnosis. Accuracy of the tumor thickness measurement by echography is an important issue with very small tumors. Wide-field photography is helpful to detect the rate of choroidal tumor growth.[7] Although these techniques have improved the diagnostic differentiation of larger size melanomas, the accuracy of diagnosis for small melanomas is more uncertain. Furthermore, smaller tumors may not produce symptoms, depending on their location with respect to the macula, and may go undetected unless discovered during the course of a routine eye examination.

The management of small choroidal melanomas is controversial. The likelihood of progression from the time of diagnosis to growth warranting treatment has not been well characterized. In the past, many ophthalmologists advocated observation. This was justified on several grounds, including the difficulty in establishing a correct diagnosis, the lack of any documented efficacy for globe-conserving treatments, and concerns for severe treatment-related morbidity. Some investigators have advocated earlier therapeutic intervention, since smaller tumor size at the time of treatment appears to be associated with lower mortality rates.[3,8,9]

The management of choroidal melanomas depends on many factors; most important are tumor size and location.[10] In otherwise healthy patients, a small choroidal melanoma in the posterior fundus is amenable to several treatment options, including radiation therapy, laser photocoagulation, transpupillary thermotherapy, a combination of these methods, or even enucleation.[10,11,12,13]

Standard treatment options:

1. Observation: Is important in patients for whom the diagnosis is uncertain or in whom tumor growth is not documented; also is prudent in asymptomatic patients with stable lesions, particularly in elderly or debilitated patients, or in patients with tumor growth in their only useful eye.[5]
2. Plaque radiation therapy: Used for small- or medium-sized uveal melanomas, amelanotic tumors, or tumors that touch the optic disc for greater than 3 clock-hours of optic disk circumference.[12,13]
3. External-beam, charged-particle radiation therapy: Provides precisely focused radiation with a homogeneous dose distribution pattern and little lateral spread; requires sophisticated equipment available only at selected centers; involves patient cooperation during treatment (voluntarily fixating the eye on a particular point so the tumor is positioned properly in the radiation beam); in eyes with tumors less than 6 mm in thickness and located more than 3 mm distant from the optic disc or fovea, clinically significant visual loss can usually be avoided.[10,12,13,14]
4. Gamma Knife radiation surgery: Is a newer method of radiation therapy; preliminary experience suggests this treatment may be a feasible option for small-sized to medium-sized melanomas.[15]
5. Laser photocoagulation: Can be used in very selected cases of small posterior choroidal melanoma; indirect ophthalmoscope laser therapy may be combined with plaque radiation therapy.[12]
6. Transpupillary thermotherapy: Causes substantial tumor necrosis in choroidal melanomas up to 3.5 mm in thickness; currently used in selected cases with deeply pigmented small choroidal melanomas in the posterior pole with minimal or no contact with the optic nerve; can be used as a primary treatment or as an adjunctive method to plaque radiation therapy.[8,9,16,17,18]
7. Local tumor resection: Used mainly for selected ciliary body or anterior choroidal tumors with smaller basal dimension and greater thickness.[19]
8. Enucleation: Is favored when severe intraocular pressure elevation is a factor; may also be considered in small- and medium-sized melanomas that are invading the tissues of the optic nerve; an eye-sparing procedure rather than enucleation should be considered if there is hope for useful vision.[11]