Clinical factors predictive of tumour cytogenetics and metastasis in 86 patients with choroidal nevus growth into melanoma (DIP and DOT study).

BACKGROUND

Choroidal melanoma can arise from malignant transformation of choroidal nevus. The Cancer Genome Atlas, a classification system based on the genetic status of chromosomes 3 and 8, can be used to prognosticate metastasis and death in choroidal melanoma. This study explores the impact that growth rates and clinical/imaging (TFSOM-DIM (To Find Small Ocular Melanoma, Doing IMaging)) risk factors have on cytogenetics, metastasis and death in choroidal nevus which transforms into melanoma.

METHODS

A retrospective study was performed on 86 consecutive patients diagnosed with choroidal nevus with transformation into melanoma. Tumour cytogenetic results and TFSOM-DIM risk factors for transformation at the date of initial presentation (DIP) and date of transformation diagnosis (DOT) were recorded. Cytogenetic testing of tumours was offered to patients at DOT and was performed on tumour samples obtained via fine-needle aspiration biopsy prior to plaque radiotherapy initiation.

RESULTS

Of 86 patients, 66% were cytogenetically low-risk and 34% were cytogenetically high-risk. At DOT, high-risk tumours possessed more TFSOM-DIM risk factors than low-risk tumours (4.5 vs 3.8, p=0.003). Choroidal nevus with growth in thickness >0.5 mm/year or >20% per year had increased risk for high-risk cytogenetics (relative risk (RR)=1.93, 95% CI 1.09 to 3.43, p=0.027; RR=2.18, 95% CI 1.22 to 3.92, p=0.008, respectively). Choroidal nevus with growth in basal diameter >0.7 mm/year or >10% per year had increased risk for high-risk cytogenetics (RR=2.22, 95% CI 1.25 to 3.93, p=0.007; RR=1.83, 95% CI 1.03 to 3.26, p=0.042, respectively).

CONCLUSIONS

When monitoring patients with choroidal nevus, clinical risk factors are important in estimating risk for transformation into melanoma. We found that thickness growth >0.5 mm/year or >20% per year, as well as basal diameter growth >0.7 mm/year or >10% per year, were all thresholds that demonstrated increased risk for high-risk cytogenetics. Additionally, tumours with a greater number of TFSOM-DIM risk factors by DOT had significantly increased likelihood of high-risk cytogenetics.