Risk factors for growth and metastasis of small choroidal melanocytic lesions

The management of small melanocytic choroidal tumors is controversial. An important reason for this controversy is that the natural course and metastatic potential of these lesions are not defined clearly. Prior studies that have attempted to elucidate the natural course of these lesions have focused on selected small groups of patients with presumed small choroidal melanomas. There are no large studies investigating the growth potential and metastatic potential for the spectrum of small melanocytic choroidal tumors when considered as an unselected whole group. In addition, the clinical features of these tumors predictive of metastases have not yet been identified.

A retrospective review was performed on 1329 patients with small melanocytic choroidal tumors measuring 3 mm or less in thickness. Clinical parameters of the patient and tumor were obtained and analyzed for their relation to eventual tumor growth and metastasis using a Cox proportional hazards regression model.

Tumor growth was documented in 18% of patients. The factors predictive of tumor growth (multivariate analysis) included greater tumor thickness (P = 0.0001), posterior tumor margin touching optic disc (P = 0.0001), symptoms of flashes, floaters (P = 0.002), and blurred vision (P = 0.003) relative to no symptoms, orange pigment on the tumor surface (P = 0.004), and the presence of subretinal fluid (P = 0.05). The relative risk (RR) was greatest for initial tumor thickness 2.1 to 3.0 mm (RR = 5.2) and tumor thickness 1.1 to 2.0 mm (RR = 4.3) relative to tumors 1 mm or less in thickness, as well as posterior margin touching the optic disc (RR = 2.6). After adjusting for significant tumor variables, the effect of interventional tumor treatment showed a decreasing risk for tumor growth compared with continued observation without treatment. Of 1329 patients, metastases developed in 35 (3%). The factors predictive of metastases (multivariate analysis) included posterior tumor margin touching the optic disc (P = 0.003), documented growth (P = 0.003), and greater tumor thickness (P = 0.004). The relative risk for metastases was greatest for tumor thickness 1.1 to 3.0 mm (RR = 8.8) and growth (RR = 3.2).

Of small choroidal melanocytic tumors measuring 3 mm or less in thickness at the time of initial examination, 18% demonstrated growth and 3% metastasized during the period of follow-up. Based on this analysis, the clinical features of these tumors can be used to estimate the risk for tumor growth and metastases and assist the clinician with patient management.