Patterns of failure in surgical therapy of medulloblastomas.

To better understand the relationship between the modalities of the surgical ablation of medulloblastomas--partial versus total tumor exeresis--and the pattern of tumoral relapse (local regrowth or metastases at distance), we have analyzed forty-five children affected by cerebellar medulloblastomas, observed at the Policlinico Gemelli, Catholic University Medical School, Section of Pediatric Neurosurgery, between 1981 and 1992. According to the entity of the surgical exeresis, the patients have been divided in three groups: group I, 25 children with complete neoplastic excision confirmed by post-surgical Computed Tomographic (CT) scans (total exeresis); group II, 11 patients with minimal tumor residual or infiltration in vital areas at the operation, known to the surgeon, but not visualized on post-operative CT examination (subtotal exeresis); and group III, 9 children with a residual tumoral mass, known to surgeon and visualized in the immediate postoperative CT scan and further confirmed in late CT controls (partial exeresis). Our results confirm that a significant difference in survival is observed among patients with total removal, compared to those with subtotal and partial tumor exeresis, so stressing the importance of even minimal (not detectable at the postoperative CT scan) tumoral brain stem infiltration. The analysis of our series shows a different local tumor recurrence rate in the three groups of patients, that appear to indicate an inverse relationship between degree of tumoral surgical resection and possibility of its local recurrence. However, even though a complete removal of the tumor appears associated with a minor figure of local recurrence, it does not appear to influence significantly the ability of the tumor to metastatize in the long run.