Relationship between rate of posterior uveal melanoma flattening following plaque radiotherapy and gene expression profile class of tumor cells.

PURPOSE: To evaluate the relationship between rate of flattening of posterior uveal melanomas (PUMs) over the first 6 months following I-125 plaque radiotherapy and gene expression profile (GEP) class of tumor cells obtained by fine needle aspiration biopsy (FNAB) prior to treatment.
METHODS: Retrospective analysis of relationship between GEP of PUM cells obtained by FNAB at or prior to treatment and rate of tumor flattening following I-125 plaque radiotherapy. Impact of initial tumor thickness was minimized by pairing cases so baseline tumor thickness in subgroups was matched to within ± 0.5 mm. Paired t-testing compared mean tumor thickness in GEP subgroups at 3- and 6-months post treatment assessments.
RESULTS: Our initial group consisted of 269 patients. Seventy-seven tumors (28.6%) were GEP class 2. Twenty-seven of these were treated by I-125 plaque radiotherapy post-FNAB and returned for post treatment evaluations at 3 and 6 months. A matched GEP class 1 tumor was identified for 25 class 2 cases. Matched tumor pairs ranged in thickness from 2.5 to 11.5 mm at baseline. Mean tumor thickness at baseline in the GEP 1 subgroup was 5.8 and 5.9 mm in the GEP 2 subgroup. Three-months post plaque, mean tumor thickness was 4.5 mm in class 1 cases and 4.6 mm in class 2 cases (paired t = 0.31, P = 0.76). The 6-month post-plaque, mean tumor thickness was 4.0 mm in each subgroup (paired t = 0.25, P = 0.81).
CONCLUSIONS: Our study showed a lack of association between the GEP class and the rate of flattening of posterior uveal melanomas following I-125 plaque radiotherapy of PUMs.