Effects of proton beam irradiation on uveal melanomas: a comparative studyof Ki-67 expression in irradiated versus non-irradiated melanomas

Aims-To assess the cellular proliferation using the monoclonal antibody Ki- 67, in paraffin embedded uveal melanomas irradiated by proton beam, as well as in non-irradiated uveal melanomas. Methods-30 enucleated eyes were included for histopathogical study and Ki-6 7 immunostaining. Patients were enucleated between 1991 and 1995 for uveal melanoma, 14 after proton beam irradiation and 16 without treatment (contro l group). The mean follow up period was 2.5 years after diagnosis and 1 yea r after enucleation. Results-A significant: relation was found between Ki-67 score and mitotic i ndex (r = 0.56, p = 0.001), histological largest tumour diameter (r = 0.38, p = 0.03), fibrosis (r = -0.35, p = 0.05), absence of tumoral pigmentation (p = 0.05), and presence of vascular thrombosis (19 0.03). The Ki-67 score was significantly higher in the non-irradiated group (p = 0.01) and in the group of patients whose cause of enucleation was tumoral evolution (p = 0. 005) compared with the group of patients enucleated after neovascular glauc oma. The Ki-67 score was very high in a case of orbital recurrence of uveal melanoma and metastatic death. 70% of metastasised tumours showed a Ki-67 score higher than the median value. Conclusion-Ki-67 labelling is a reliable method of estimating the prolifera tive activity in uveal melanomas after proton beam irradiation. The Ki-67 s core is significantly correlated with prognostic variables (mitotic index a nd histological largest tumour diameter), and with radiation effects after proton beam irradiation.