Analysis of radiation failure after uveal melanoma brachytherapy

We analyzed the number of cycling cells in the DNA synthesis phase and in mitosis in two uveal melanomas unsuccessfully treated with iodine 125 brachytherapy. In one patient, the tumor appeared to have been radioresistant, whereas the other patient had a clinically inapparent area of tumor that was not included in the tumoricidal radiation field. In the first patient, there was uniform tumor cell cycling, whereas the second patient had cycling cells predominantly in the area that did not receive optimal radiation. This gradient of cycling tumor cells in the second patient was observed with both standard histologic examination (mitoses per high-powered field) and bromodeoxyuridine staining (DNA synthesis). The bromodeoxyuridine technique was significantly more sensitive than standard histologic examination in the detection of cycling cells.