The molecular landscape and associated clinical experience in infant medulloblastoma: prognostic significance of second‐generation subtypes
Debbie Hicks, Gholamreza Rafiee, Ed C. Schwalbe, C. I. Howell, Janet C. Lindsey, Robert M. Hill, Amanda Smith, Peter Adidharma, Catherine Steel, Sarah J. Richardson, Lori J. Pease, Marina Danilenko, S Crosier, Abhijit Joshi, Stephen B. Wharton, Thomas S. Jacques, Barry Pizer, A. Michalski, Daniel Williamson, Simon Bailey, S. C. Clifford
Abstract
Aims Biomarker‐driven therapies have not been developed for infant medulloblastoma (iMB). We sought to robustly sub‐classify iMB, and proffer strategies for personalized, risk‐adapted therapies. Methods We characterized the iMB molecular landscape, including second‐generation subtyping, and the associated retrospective clinical experience, using large independent discovery/validation cohorts (n = 387). Results iMB Grp3 (42%) and iMB SHH (40%) subgroups predominated. iMB Grp3 harboured second‐generation subtypes II/III/IV. Subtype II strongly associated with large‐cell/anaplastic pathology (LCA; 23%) and MYC amplification (19%), defining a very‐high‐risk group (0% 10yr overall survival (OS)), which progressed rapidly on all therapies; novel approaches are urgently required. Subtype VII (predominant within iMB Grp4 ) and subtype IV tumours were standard risk (80% OS) using upfront CSI‐based therapies; randomized‐controlled trials of upfront radiation‐sparing and/or second‐line radiotherapy should be considered. Seventy‐five per cent of iMB SHH showed DN/MBEN histopathology in discovery and validation cohorts ( P < 0.0001); central pathology review determined diagnosis of histological variants to WHO standards. In multivariable models, non‐DN/MBEN pathology was associated significantly with worse outcomes within iMB SHH . iMB SHH harboured two distinct subtypes (iMB SHH‐I/II ). Within the discriminated favourable‐risk iMB SHH DN/MBEN patient group, iMB SHH‐II had significantly better progression‐free survival than iMB SHH‐I , offering opportunities for risk‐adapted stratification of upfront therapies. Both iMB SHH‐I and iMB SHH‐II showed notable rescue rates (56% combined post‐relapse survival), further supporting delay of irradiation. Survival models and risk factors described were reproducible in independent cohorts, strongly supporting their further investigation and development. Conclusions Investigations of large, retrospective cohorts have enabled the comprehensive and robust characterization of molecular heterogeneity within iMB. Novel subtypes are clinically significant and subgroup‐dependent survival models highlight opportunities for biomarker‐directed therapies.