[Medulloblastoma: towards new prognostic factors]

Abstract

Current therapeutic protocols for medulloblastoma combining, with surgery, radiation therapy and chemotherapy allow 5-year survival rates of over 50%. However these therapies induce mainly in children long-term adverse effects, which produce a therapeutic dilemma emphasizing the need for reliable prognostic factors in order to adapt the treatment modalities to the degree of the tumor's aggressiveness. Contradictory results have been reported concerning the conventional clinical and histological prognostic factors in medulloblastoma. Recent development and simplification of cell biology technologies could now help in the resolution of this issue. The aim of this review is to present some new prognostic factors available from these advances, and to discuss their potential usefulness in the field of medulloblastoma: The measurement of the proliferative potential of tumors using thymidine analogues such as bromodeoxyuridine (BUdR), or the monoclonal antibody Ki-67 is promising. The flow cytometric determination of D.N.A. content in medulloblastomas appears to show a correlation of diploidy with a worse prognosis than aneuploidy. Modern cytogenetic and molecular biology techniques are permitting the current assessment of amplification and overexpression of oncogenes, or the presence of deletions, as prognostic factors in medulloblastoma. The study of the cellular phenotype and particularly the search for differentiation markers has not yet led to clear-cut results from a prognostic viewpoint, but further advances are to be expected in this field, thanks to the development of more specific monoclonal antibodies. The investigation of the tumoral stroma and metabolism is very promising too. These novel approaches to prognostic factors in medulloblastoma should allow a better classification and management of these tumors in the near future.