Proliferation not apoptosis as a prognostic indicator in retinoblastoma

The balance between proliferation and cell death is the major determinant o f tumour growth. We analysed the proliferative and apoptotic indices (PI an d AI, respectively) of 33 children with retinoblastoma. PI and AI were asse ssed by immunohistochemistry for Ki-67 antigen and TUNEL staining, respecti vely. The mean PI was 21.0+/-21.1%, and higher PI was associated with more advanced tumour stage (P<0.0001) and poor clinical outcome (P<0.05). Patien ts in whom amplified N-myc oncogene was found (n=6) determined by the multi plex polymerase chain reaction tended to have a higher PI (37.6+/-27.2%) th an those without amplified N-myc (n=27; PI=17.3+/-18.1). A PI value of over 40% was clearly associated with an unfavourable prognosis. The AI, however , did not correlate with any of the other variables analysed. The findings suggest that proliferation, but not apoptosis, is of critical significance in retinoblastoma biology. PI, as determined by the Ki-67 antigen labelling index, seems to be a relevant histopathological parameter that can predict the clinical outcome of retinoblastoma.