PROGNOSTIC FACTORS IN ADULT MEDULLOBLASTOMA - A CLINICOPATHOLOGICAL STUDY

Aims and background Medulloblastoma in adults is a rare tumor. The sma ll number of cases in the reported series has not permitted a definite assessment of the prognostic role of clinical, pathologic and cell ki netics factors, The largest series of medulloblastoma in adults treate d in a single institution is herein reported, Methods. The clinical, t herapeutic, pathologic and proliferation features of medulloblastoma i n 44 adult patients (> 18 years) were analyzed retrospectively with re gard to postoperative survival. The proliferation potential of each tu mor was evaluated by the immunohistochemical demonstration of prolifer ating cell nuclear antigen (PCNA) and Ki-67, clone MIB-1, in paraffin sections. Results. The overall 5- and 10-year survival rates were 40% and 35.6%, respectively. Significant factors in predicting a longer po stoperative survival were: age < 37 years, decade of management (1977- 1990), radiotherapy (50-55 Gy on the posterior fossa and 30-35 Gy on t he spinal cord) and nuclear isomorphism. When corrected for adequacy o f radiotreatment, desmoplastic type and differentiation were significa ntly correlated with a shorter survival. The PCNA-labelling index (LI) ranged from 34.5 to 82.2%, the MIB-1-LI ranged from 9.6 to 64.7%. No association was found between PCNA- or MIB-1-LI values and microscopic features, or between LI values and prognosis. Conclusions. Contrary t o a general assumption, desmoplastic medulloblastoma and differentiate d medulloblastoma are negative prognostic factors in adequately radiot reated adult patients. This may possibly be referred to lower radiosen sitivity of these tumor variants. The LI with PCNA or Ki-67 is of no h elp in identifying aggressive tumors.