Tumor size confirmed as a risk factor for metastasis in patients with uveal melanoma

A retrospective chart review of patients with uveal melanoma confirmed that basal diameter is an independent risk factor for metastasis in patients with class 2 tumors and was the only significant difference in those who developed metastasis.

Study design

A retrospective chart review of patients with uveal melanoma who underwent successful gene expression profile (GEP) testing and were treated with plaque brachytherapy at the University of Iowa and plaque brachytherapy, enucleation, or other approaches at the Cleveland Clinic was performed. Clinical information, molecular prognostication, and metastasis and survival information were documented. A meta-analysis of published studies reporting metastasis-free survival in patients with class 2 uveal melanoma at 3 and 5 years was conducted.

Outcomes

In the study cohort, most patients with metastasis had class 2 tumors (40/48). In looking at all class 2 tumors, patients who developed metastasis had larger tumors than those who did not, but no other significant differences were identified. Comparing the cohort from this study and the meta-analysis of published series to the predicted metastasis-free survival rate, those from the study and published literature demonstrated a better observed metastasis-free survival rate.

Limitations

The study mentions that there are differences in the baseline characteristics of this study with the Collaborative Ocular Oncology Group (COOG) Study that the predicted rate of metastasis for class 2 tumors comes from. Patients in the COOG study had larger tumors at baseline, which has been shown in multiple studies to affect the rate of metastasis, including in the current study. This study mentions that prognostic information has been used to identify at-risk individuals who could be offered adjuvant therapy and suggests that a better prognosis noted in published studies compared to predictions may affect clinical trial criteria. However, some clinical trials exploring adjuvant therapy for high-risk patients based on GEP have already included largest basal diameter requirements to identify the most high-risk patients.

Clinical significance

While this study does not currently impact clinical decision making, it is an important reminder that not all class 2 uveal melanomas are the same. Largest basal diameter is an important independent risk factor that affects prognostication. Other risk modifiers include the presence of preferentially expressed antigen in melanoma (PRAME), which is being evaluated prospectively by the COOG2 study. Perhaps the inclusion of PRAME analysis and largest tumor diameter in the algorithm for prognostication will yield more accurate metastasis-free survival results in the future.