Population-based assessment of clinical characteristics predicting outcome of conjunctival melanoma in whites

Abstract

Purpose: To identify the clinical determinants of prognosis and the incidence of malignant conjunctival melanoma in whites.

Methods: A nationwide search identified 85 patients in whom primary conjunctival melanoma was diagnosed in Finland between 1967 and 2000, all of whom were enrolled. Data were collected from the Finnish Cancer and Population Registries and from patients' charts in all involved hospitals. The age-specific and age-adjusted incidences were calculated. Clinical characteristics of the tumors were recorded and time to local recurrence and melanoma-specific survival were analyzed by Kaplan-Meier analysis and univariate and multivariate extended Cox regression.

Results: The annual crude incidence of conjunctival melanoma in Finland was 0.51 per million inhabitants, and the age-adjusted incidence (mean, 0.54) increased from 0.4 to 0.8 during the 34-year study period. The median age at diagnosis was 60 years (range, 20-90). Clinically detectable primary acquired melanosis preceded or accompanied the primary tumor in 61% of patients. The 5-year cumulative proportion of cases with local recurrence was 0.36 (95% confidence interval [CI], 0.25-0.48). The melanoma-specific 5-and 10-year mortalities were 0.20 (95% CI, 0.12-0.32) and 0.38 (95% CI, 0.26-0.53), respectively. By multiple-event Cox regression, nonlimbal location of the primary tumor predicted a short time to local recurrence (hazard ratio [HR] 1.81, P = 0.024). Nonlimbal location of the primary tumor (HR 4.08, P = 0.023) and increasing tumor thickness (HR 1.19 for each millimeter change, P=0.063) were associated with increased mortality. Local recurrence, analyzed as a time-dependent covariate, also increased mortality (HR 1.39 for each recurrence, P = 0.014).

Conclusions: The incidence of conjunctival melanoma in the white population of Finland increased analogous to cutaneous melanoma. Nonlimbal tumors recur more often and are associated with decreased survival, independent of their greater thickness. Local recurrence contributes to mortality, whereas primary acquired melanosis was not associated with either outcome.