Purpose: To study the pattern of metastasis and overall survival in patients with disseminated conjunctival melanoma.
Design: Population-based, retrospective cross-sectional study.
Participants: Eighty-five Caucasian patients with primary malignant conjunctival melanoma diagnosed between 1967 and 2000.
Methods: Data were collected from the Finnish Cancer and Population Registries and all involved hospitals. The pattern (regional or systemic) and site of first metastasis were recorded. The time to first metastasis and survival by pattern were estimated by cumulative incidence analysis, which takes competing risks into account, and by Kaplan-Meier analysis, respectively.
Main outcome measures: Metastatic pattern, time to metastasis by pattern, overall survival.
Results: In 45% (95% confidence interval, 23%-68%) of 20 patients with metastasis, regional lymph node metastases were detected before systemic ones. Median times to initial regional and systemic metastasis were 2.3 and 3.4 years, respectively, and the median time from regional to systemic metastasis, 1.0 year. The 10-year cumulative incidence of initial regional metastasis was 0.11, and it tended to be higher for tumors more than 2 mm thick (0.18 vs. 0.05, P = 0.062). The corresponding incidence of initial systemic metastasis was 0.18, and it was higher for nonlimbal tumors (0.38 vs. 0.07, P = 0.00023) and for tumors more than 2 mm thick (0.28 vs. 0.06, P = 0.026). Overall survival was longer after initial regional metastasis than after systemic metastasis (30 vs. 8 months, P = 0.012).
Conclusion: Initial regional lymph node metastasis was as common as systemic metastasis, but initial lymph node metastasis was associated with better prognosis. Metastasis, especially initial regional lymph node metastasis, from limbal tumors and tumors less than 2 mm thick was rare. These patients may have less benefit from sentinel lymph node biopsy, a method that is currently under evaluation regarding its potential to improve survival.