A histologic study (including DNA quantification and Ki-67 labeling index) in uveal melanomas after brachytherapy with ruthenium plaques.

PURPOSE: To investigate the proliferative potential and DNA damage in uveal melanomas treated by brachytherapy.
METHODS: Forty-two enucleated eyes that had been treated with 106Ru/106Rh radioactive plaques for uveal melanoma were subgrouped according to the extent of irradiation damage. Cell proliferation was determined by immunoreactivity for the proliferation marker Ki-67 (Mib-1) and ploidy by quantitative DNA image analysis. Thirty globes containing uveal melanomas without prior brachytherapy served as a control group.
RESULTS: The values for Ki-67 reactivity and ploidy could be correlated with radiation-induced changes within the tumors. In regions of the tumor where complete exposure to the prescribed radiation dose was assumed from the histologic findings, the Ki-67 index was close to or equal to zero. Hypoploidy was exclusive to irradiated tumors and was most often detected in effectively irradiated regions. Tumor regions classified as partially irradiated or recurrent showed an increase of Ki-67 indices and DNA content. Values obtained in recurrent tumors did not significantly differ from the control group.
CONCLUSIONS: Tumor cell proliferation and variations in ploidy status could be detected after brachytherapy, but the response varied markedly both within individual tumors and within the irradiated group. Evidence of persisting proliferative potential could be obtained in ostensibly sterilized tumor tissue, but a negligible Ki-67 index and the presence of hypoploidy were considered to be reliable indicators for radiation-induced loss of proliferative potential.