Surveillance imaging in children with medulloblastoma (posterior fossa PNET)

Background. The use of surveillance imaging in children with medulloblastoma has been criticised. The aim of this study was to determine what proportion of relapses are detected by surveillance and whether these are found at a relatively favourable stage. Methods. This study was a retrospective review of the medical charts and imaging studies of 89 patients treated at a single children's cancer centre. Relapse was defined as evidence of an increase in volume of residual tumour of greater than 25 % or the presence of metastases, or new onset of positive CSF cytology. Relapse was termed symptomatic if it was diagnosed by tests performed because of new symptoms that occurred in the interval between surveillance examinations. Asymptomatic relapse was diagnosed solely on the basis of surveillance imaging. Survival time to relapse was calculated from the date of the first surgical procedure. Results. Surveillance imaging detected 17 (71%) of the 24 relapses that occurred later than 6 months after diagnosis. All seven patients who presented with symptoms between scans have died, with a median survival from relapse of 5 months. Median survival from relapse in the patients detected by surveillance was 44 months, and four remain alive at 44-75 months. The patients detected by surveillance tended to have less advanced disease, which was more amenable to salvage therapy. Conclusion. This type of study cannot prove that surveillance imaging improves survival in children with medulloblastoma because of the effects of lead time and length biases. Despite this, surveillance does appear to be effective in detecting potentially curable medulloblastoma relapses and should be offered to all patients.