Prognosis of Non-Metastatic Choroidal Melanoma
The prognosis of choroidal melanoma without metastatic spread is generally favorable but varies significantly based on tumor size, with small tumors (<4mm thickness) showing 84% metastasis-free survival at 5 years, while larger tumors have progressively worse outcomes. 1
Prognosis by Tumor Size
The most critical prognostic factor for non-metastatic choroidal melanoma is tumor thickness (Breslow index equivalent):
- Small melanomas (<4mm thickness): 16% develop metastasis at 5 years (84% metastasis-free survival) 1, 2
- Medium melanomas (4-8mm thickness): 32% develop metastasis at 5 years 1, 2
- Large melanomas (>8mm thickness): 53% develop metastasis at 5 years 1, 2
For very small choroidal melanomas (≤3mm thickness), the prognosis is excellent with melanoma-related mortality of 0% at 3 years, 1.7% at 5 years, 5.1% at 10 years, and 10.2% at 15 years. 3
Treatment Outcomes for Small Tumors
When treated with modern brachytherapy techniques:
- Visual acuity of 20/50 or better is maintained in 69% of patients at 3 years 4
- Local tumor control rate is 99% with only 1% recurrence 4
- Ocular survival (eye preservation) rate is 99.3% 4
- No metastatic events observed at 3 years in optimally treated small tumors 4
Critical Timing Considerations
Metastasis can occur quite early when tumors reach approximately 3.0mm basal dimension and 1.5mm thickness, emphasizing the importance of early detection and treatment. 2 However, even with early effective local treatment, metastasis can develop late in the disease course, with an average time from treatment to metastasis detection of 7 years (range 3.9-12 years). 3
Factors Beyond Tumor Size
Survival prognosis correlates not only with clinical stage but also with histologic grade, genetic type (particularly monosomy 3), and competing causes of death. 5 The overall mortality rate for choroidal melanoma is approximately 50%, primarily due to metastatic disease involving the liver. 5
Common Pitfalls
- Assuming all small tumors are benign: Small melanomas still carry a 16% metastasis risk at 5 years, requiring definitive treatment rather than observation alone 1
- Inadequate long-term surveillance: Metastases can develop over a decade after initial treatment, necessitating lifelong monitoring 3
- Relying solely on tumor size: Genetic factors and histologic features significantly modify prognosis and should be incorporated into risk assessment 5