Medulloblastoma. The identification of prognostic subgroups and implications for multimodality management.

For 43 medulloblastoma patients who had five-and ten-year actuarial survival rates of 56%, prognostic factors of statistical significance included: T-stage (82% T1,2 versus 46% T3,4; P less than 0.02), M-stage (63% M0,1 versus 0% M2,3; P less than 0.03), and histopathologic tumor score (TS, based upon necrosis, desmoplasia, cytoplasmic processes, and mitoses) (81% TS less than or equal to 5 versus 41% TS greater than or equal to 6; P less than 0.05). Posterior fossa local control rates were also function of T-stage (90% T1,2 versus 38% T3,4) and TS (83% TS less than or equal to 5 versus 38% TS greater than or equal to 6). Combining TS with T-stage, patients fell into three prognostic and local control groups, which may have different future management implications: Small (T1,2) tumors of favorable (TS less than or equal to 5) histology had a 92% ten-year actuarial survival rate with 100% (8/8) local control; no change from current management is suggested. For the intermediate prognosis group (T1,2-TS greater than or equal to 6 or T3,4-TS less than or equal to 5 with 67% and 70% survival, respectively), increasing the irradiation dose alone may improve survival because these tumors exhibited an irradiation dose-response relationship. However, it is the poor prognosis group (T3,4-TS greater than or equal to 6 with 42% survival) which might be suitable for future adjuvant chemotherapy or radiosensitizer trials since there is no evidence that higher irradiation doses improve local control. This article identifies prognostic subgroups based on histologic type and TM staging in medulloblastoma patients which potentially may be utilized to improve therapeutic results, and confirms the value of staging patients with central nervous system malignancies.