Abstract Date: 4/8/2014
Eric M. Thompson, MD (Toronto, Canada)
Michael Taylor, MD, PhD (Toronto)
Medulloblastoma is now acknowledged to comprise 4 distinct molecular subgroups (WNT, SHH, Group 3, and Group 4) that are clinically and genetically distinct. Traditionally, increased extent of resection (EOR) has been associated with improved prognosis for medulloblastoma. This study sought to determine the clinical importance of EOR and metastatic stage by medulloblastoma subgroup.
Medulloblastoma subgroup affiliation was determined using nanosString profiling. Extent of resection was classified as gross total (GTR), near total (NTR,<1.5cm2), or subtotal (STR,≥1.5cm2) based on post-operative contrast-enhanced CT or MRI. Presence (M+) or absence (M0) of metastases was determined at initial staging. Mantel-Cox log-rank was used to compare overall survival (OS) and ANOVA to compare EOR.
We analyzed 518 medulloblastoma samples: 55 WNT, 150 SHH, 108 Group 3, and 205 Group 4. There was no difference in distribution of GTR, NTR, STR between the 4 subgroups (P=0.3126). Increased EOR was associated with increased OS only in Group 4 patients (P=0.0118). For the M0 subset of patients, EOR was associated with OS only in Group 4 patients (P=0.0055). Extent of resection had no impact on OS in patients with metastasis (M+) regardless of subgroup. M+ patients had a worse OS than M0 patients in the SHH group (P=0.0191) and Group 4 (P=0.0455).
Obtaining a GTR has prognostic significance only in Group 4 patients. Intraoperative medulloblastoma subgrouping will guide surgical resection in the near future. EOR has no impact on M+ patients regardless of subgroup and aggressive surgical resection should not be attempted at the cost of potential morbidity.
Article ID: AA-28593