Therapy and biomarker dependent progression-free survival in infant sonic hedgehog medulloblastoma: a multi-national...

Medulloblastoma in infants (iMB; aged < 5 years) presents the challenge of achieving cure while minimising deleterious cranio-spinal irradiation (CSI)-associated late-effects. Non-randomised phase 2 studies have examined upfront CSI omission and chemotherapy intensification for favourable-risk desmoplastic/nodular (DN) tumours associated with the sonic hedgehog (SHH) molecular group (iMB_SHH). Comparison of these therapies in large molecularly defined iMB_SHH cohorts, alongside investigations of prognostic biomarkers in therapy-specific context, is urgently required to define future therapeutic strategies.

In this international retrospective cohort study, a multi-national cohort of molecularly and clinically annotated iMB_SHH was assembled from patient datasets in nine countries. Inclusion criteria was a principal iMB_SHH group classification using DNA methylation array-based classification. Patient cohorts were assigned into upfront treatment groups based on the receipt of radiotherapy (RTx) or chemotherapy (CTx)-only. Upfront RTx treatment groups were assigned as those receiving focal-RTx or CSI. Upfront CTx only regimens used were classified into three groups to reflect disease treatment conventions: standard-dose, high-dose (intensified regimens of sufficient dosage to require stem cell support) and those including intraventricular methotrexate (IVT-MTX). We investigated molecular pathology, upfront treatments, and relationships to outcome, in this real-world setting. Outcomes of interest were progression-free survival (PFS), overall survival (OS), and post-relapse survival (PRS).

Between January 20, 2018 and October 6, 2021, patient data from 267 infants with SHH medulloblastoma were collected from Canada (n = 74), Germany/USA (n = 67), and the UK (n = 54), alongside national cohorts collected from France (n = 26), Italy (n = 4), Japan (n = 20), the Netherlands (n = 11), and Spain (n = 33). 226 patients with PFS and OS data comprised the iMB survival cohort and were split into upfront treatment groups based on the receipt of RTx (n = 74, 33%) or CTx-only (n = 132, 58%). Among iMB_SHH patients treated upfront with CTx-only regimens, IVT-MTX therapy (5-year PFS, 72.6%; n = 72) or high-dose therapy (73.0%; n = 29) achieved PFS outcomes comparable to upfront CSI-based regimens (n = 49; 74.0%; p = 0.51); whereas lower-intensity, standard-dose, chemotherapy-only regimens (n = 31) were inferior (48.4% PFS; p = 0.006). Rescue was common post-relapse after IVT-MTX/high-dose protocols and translated into 5-year OS of 85.6% and 88.6%, respectively. However, information on pattern of relapse and treatments received at recurrence was only available for a small proportion of our cohort (n = 43). The 5-year PFS of patients receiving focal-RTx was (58.2%; n = 25). iMB_SHH encompassed SHH-1 (38%), SHH-2 (47%) and SHH-3 (14%) WHO subgroups. In CSI-naïve iMB_SHH, standard-dose chemotherapy was associated with worse PFS in SHH-1 (p = 0.001), but not SHH-2. Non-DN/MBEN histology (21.2% of iMB_SHH) conferred worse PFS in the upfront CSI-treated and standard-dose (p < 0.001 and p = 0.003, respectively) groups. Metastatic disease only associated with prognosis with upfront IVT-MTX-only therapies (p = 0.013), while established high-risk features of non-infant MB_SHH (TP53-mutation, LCA-histology, MYCN-amplification) only associated with poor prognosis in older SHH-3 (7/7 relapsed). Finally, CSI-naïve PFS findings were validated in a re-evaluation of smaller historical trials cohorts.

Our findings show that iMB_SHH outcomes and prognostic biomarkers are therapy dependent. In our retrospective patient group, non-metastatic iMB_SHH treated with high-dose or IVT-MTX chemotherapy-only had equivalent favourable outcomes, independent of histology and subgroup. With outcomes established, clinical trials are now encouraged to focus on quality-of-life following different intensified approaches to identify the kindest curative strategies.

Cancer Research UK, Children with Cancer UK, Children's Cancer North, Star for Harris, JGW Patterson Foundation, Little Hero and Blue Skye Thinking.