Clinical characteristics, treatment outcomes and prognostic factors for metastasis in stage 1 choroidal melanoma: a retrospective cohort study in 159 patients.

Objective: To investigate the clinical characteristics, risk factors, and treatment outcomes of stage 1 choroidal melanoma (CM) and to identify prognostic indicators for metastasis.

Design: A retrospective cohort study.

Participants: Consecutive patients diagnosed with stage 1 CM at Beijing Tongren Hospital.

Methods: Tumours were classified according to the American Joint Committee on Cancer Cancer Staging Manual, 8th edition. Clinical, demographic, and treatment data were analyzed, focusing on tumour size, shape, subretinal fluid, and treatment responses. Kaplan-Meier analysis and a nomogram were used to assess metastatic-free survival and identify prognostic factors.

Results: This retrospective study analyzed 159 patients with stage I CM to identify metastasis predictors and therapeutic response patterns. With a median follow-up of 78 months, 5.7% (9/159) developed metastases, showing metastasis rates of 0.63%, 3.23%, and 7.89% at 1, 5, and 10 years, respectively. Univariate analysis revealed the largest basal diameter (LBD), subretinal fluid, and irregular tumour shape as potential risk factors for metastasis. A nomogram model integrating LBD, morphology, and subretinal fluid demonstrated superior predictive performance compared to LBD alone (area under the curve = 0.84 vs 0.71). Metastatic cases are more likely to exhibit a "decrease-then-increase" treatment response within 24 months. The median metastasis-free interval was 49 months (range: 10-81), and postmetastasis survival averaged 22.6 months.

Conclusions: The largest basal diameter, irregular shape, subretinal fluid, and a "decrease-then-increase" treatment response pattern are identified as key predictors of metastasis in stage 1 CM. These findings underscore the importance of risk stratification and close monitoring of high-risk patients.