Appraisal of the current staging system for residual medulloblastoma by volumetric analysis

Abstract

This study aims to investigate the accuracy of the current staging system of childhood medulloblastoma by using volumetric image analysis on immediate post-operative MRI scans. Tumour volume and maximum cross area of residual medulloblastoma were measured on immediate post-operative MR scans of 37 children operated between 1999 and 2005. Mean preoperative volume was 32cm(3) (range 4.5-71.9cm(3)). Mean post-operative volume was 3.3cm(3) (range 0-23.3cm(3)). At mean follow-up of 50.08months (range 6-129), 15 (40%) patients had died. Cut-off limit for residual post-operative tumour volume employed was maximum cross section of 1.5cm(2), which corresponds to volume of 1.376cm(3); 14 patients (38%) had no residual tumour, 7 patients (19%) had less than 1.5cm(2) and 16 patients (43%) had more than 1.5cm(2) residual tumour in its maximum cross section area. In three patients (8.2%) there was mismatch between the measured maximum cross section area and volume. In particular, in two patients, the cross section areas were more than 1.5cm(2) but the residual tumour volumes were less than 1.376cm(3) (the cross section area overestimated the residual volume) and in one case, the cross section area was less than 1.5cm(2) but the residual tumour volume was more than 1.376cm(3) (the cross section area underestimated the residual volume; difference statistically significant, Fisher's exact test, p < 0.01). It appears that volumetric measurement of residual medulloblastoma on immediate post-operative MRI scans may further improve the accuracy of staging process.