Second Look Surgery for Treatment of Medulloblastoma: A retrospective analysis

Introduction: The most common malignant pediatric brain tumor is a medulloblastoma (MB). Current treatment paradigms for MB involve safe maximal surgical resection, chemotherapy, and radiation. The role of extent of resection for MB risk stratification remains less well defined. In fact, the prognostic implications of a clear surgical cutoff are controversial, but current standards rely on > 1.5 cm2 residual tumor as a high-risk measure. In some situations, undergoing a second-look surgery with the goal of obtaining a GTR, may be warranted. The objective of this study was to determine the parameters warranting a second-look surgery and access the outcomes of second-look surgery in regard to safety, patient benefit and long-term outcome.

Methods: This study was approved the Mayo Clinic Institutional Review Board (IRB). A search was conducted using the Mayo Clinic DataExplorer to identify MB patients who fit the inclusion criteria: pathology confirmed medulloblastoma diagnosis, age < 21 years at diagnosis, diagnosis date between January 1, 2003 to January 1, 2023. A retrospective chart analysis was then conducted on qualifying patients.

Results: The MayoExplorer Database yielded 93 patients who met the inclusion criteria, of these, 89% of patients received a GTR while 11% (10 patients) had a NTR/STR. Six of the 10 patients underwent a second-look surgery. Five of 6 patients achieved GTR with mild side effects such as ataxia that resolved with time. Five of 6 patients were found to have a non-WNT, non-SHH subtype of MB (the other was prior to subtyping) and subsequently went on various therapeutic protocols following recovery from surgery. Two of these patients, both who achieved GTR, had disease recurrence and ultimately succumbed to disease. In the 4 patients STR/NTR patients, only one patient had a residual tumor volume > 1.5cm2.

Conclusion : Second look surgery is safe and 83% of patients achieved GTR. Future analyses will assess factors like residual tumor location and subgroup on decision to proceed to second look surgery as well as how second look surgery may contribute to overall survival.