Radiation-Induced Apoptosis in Malignant Uveal Melanomas

Abstract

Purpose:: Radiotherapy for uveal melanoma is a treatment modality intended to preserve eye and vision. The goal of this approach is to manage local tumor control by inducing cell death in neoplastic cells. Aim of this study was to investigate the rate of cell death after stereotactic radiotherapy using a linear accelerator.

Methods:: Seventeen specimens of seventeen consecutive patients with malignant uveal melanoma who had undergone radiotherapy followed by endoresection and/or enucleation (group A) were examined with the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) method to detect apoptotic cells. As control group ninteen specimens of nineteen consecutive patients with malignant uveal melanoma who were treated by endoresection without prior radiotherapy (group B) were studied in the same manner. The mean apoptotic index (AI,%) was calculated by counting the cells in three high-power fiels (x400). Mann-Whitney U-test was used for statistical comparison.

Results:: Apoptotic cells could be found in 13 of 17 (76%) uveal melanomas of group A. The mean apoptotic index in this group was 0.18% (range:0-0.76%). In group B 8 of the 19 (42%) tumors showed apoptotic cells. The mean apoptotic index in group B was 0.05% (range:0-0.56%). Comparison of both groups referring to the apoptotic index showed a significant (p=0.0089) higher apoptotic index in the first group.

Conclusions:: Radiotherapy induces an increase in apoptosis in uveal melanomas in comparison to non-treated tumors. Nevertheless the rate of apoptosis is low in comparison to other malignant tumors.

Keywords: melanoma • radiation therapy • immunohistochemistry