Optimising prediction of early metastasis-free survival in uveal melanoma using a four-category model incorporating gene expression profile and tumour size

Background Largest basal diameter (LBD) appears to have independent prognostic value in uveal melanoma (UM). Methods All patients undergoing plaque brachytherapy or enucleation for UM involving the choroid and/or ciliary body between 2012 and 2019. Results A total of 348 patients with a mean age of 60 +/- 14 years were included and followed for a mean of 40 +/- 26 months (3.3 +/- 2.2 years). On multivariate analysis, LBD >12 mm remained a significant independent predictor of metastasis for both class 1 (HR 21.90; 95% CI 2.69 to 178.02; p=0.004) and class 2 (HR 2.45; 95% CI, 1.03 to 5.83; p=0.04) tumours. Four prognostic groups were created: group 1 (class 1, LBD <12 mm), group 2 (class 1, LBD >= 12 mm), group 3 (class 2, LBD <12 mm) and group 4 (class 2, LBD >= 12 mm). Life tables were used to calculate the 3-year and 5-year metastasis-free survival: group 1 (98 and 98%), group 2 (86 and 86%), group 3 (81 and 62%) and group 4 (54 and 47%). Compared with the reference category (group 1), the Cox proportional hazard model demonstrated a significant worsening of survival for each progressive category (group 2 (HR 21.59; p=0.004), group 3 (HR 47.12, p<0.001), and group 4 (HR 114.24; p<0.001)). In our dataset, the four-category Cox model performed poorer compared with the American Joint Committee on Cancer (AJCC) and gene expression profile (AJCC+GEP) in the Akaike's information criteria (AIC) (297 vs 291), fit better with the Bayesian information criteria (BIC) (309 vs 313) and performed similarly with the Harrel's C (0.86 (95% CI 0.80 to 0.91) vs 0.89 (0.84 to 0.94), respectively). Conclusions Combination of GEP and LBD allows separation of patients into four easy-to-use prognostic groups and was similar to a model combining AJCC stage with GEP.