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Published on: September 20, 2019
The Alliance AMBUSH Trial: Rationale and Design
Anita Mahajan1, Helen Shih2, Marta Penas-Prado3
1Department of Radiation Oncology, Mayo Clinic, Rochester, MN 55905, USA.
Abstract:
Unlike medulloblastoma (MB) in children, robust prospective trials have not taken place for older patients due to the low incidence of MB in adults and adolescent and young adults (AYA). Current MB treatment paradigms for older patients have been extrapolated from the pediatric experience even though questions exist about the applicability of these approaches. Clinical and molecular classification of MB now provides better prognostication and is being incorporated in pediatric therapeutic trials. It has been established that genomic alterations leading to activation of the sonic hedgehog (SHH) pathway occur in approximately 60% of MB in patients over the age of 16 years. Within this cohort, protein patched homolog (PTCH) and smoothened (SMO) mutations are commonly found. Among patients whose tumors harbor the SHH molecular signature, it is estimated that over 80% of patients could respond to SHH pathway inhibitors. Given the advances in the understanding of molecular subgroups and the lack of robust clinical data for adult/AYA MB, the Alliance for Clinical Trial in Oncology group developed the AMBUSH trial: Comprehensive Management of AYA and Adult Patients with Medulloblastoma or Pineal Embryonal Tumors with a Randomized Placebo Controlled Phase II Focusing on Sonic Hedgehog Pathway Inhibition in SHH Subgroup Patients (Adult & Adolescent MedulloBlastoma Using Sonic Hedgehog Trial). This trial will enroll patients 18 years of age or older with MB (any molecular subgroup and risk stratification) or pineal embryonal tumor. Patients will be assigned to one of three cohorts: (1) average risk non-SHH-MB, (2) average risk SHH-MB, and (3) high risk MB or pineal embryonal tumors. All patients will receive protocol-directed comprehensive treatment with radiation therapy and chemotherapy. Patients with SHH-MB in cohort 1 will be randomized to a smoothened inhibitor or placebo as maintenance therapy for one year.
Insights
Adult and adolescent medulloblastoma (MB) treatment lacks trials. The AMBUSH trial investigates sonic hedgehog (SHH) pathway inhibitors for SHH-subtype MB in patients aged 18+, aiming to improve outcomes for this rare adult cancer.
Area of Science:
- Neuro-oncology
- Clinical trial design
- Molecular oncology
Background:
- Medulloblastoma (MB) treatment for adults and adolescent and young adults (AYA) is largely based on pediatric protocols due to low incidence, despite potential differences in applicability.
- Molecular classification, particularly the sonic hedgehog (SHH) pathway activation (found in ~60% of MB in patients >16 years), offers improved prognostication and targeted therapy potential.
- SHH pathway inhibitors show promise, with over 80% of SHH-subtype MB patients potentially responding.
Purpose of the Study:
- To evaluate the efficacy of sonic hedgehog (SHH) pathway inhibition in adult and AYA patients with SHH-subtype medulloblastoma (MB).
- To establish a robust clinical trial framework for adult/AYA MB, addressing the lack of specific prospective studies.
- To compare SHH pathway inhibitor maintenance therapy against placebo in average-risk SHH-MB patients.
Main Methods:
- The AMBUSH trial (Adult & Adolescent MedulloBlastoma Using Sonic Hedgehog Trial) is a Phase II randomized, placebo-controlled study.
- Enrollment includes patients aged 18+ with MB (any subgroup/risk) or pineal embryonal tumors, stratified into three cohorts.
- Average-risk SHH-MB patients (Cohort 1) are randomized to receive either a smoothened inhibitor or placebo as maintenance therapy for one year, alongside standard radiation and chemotherapy.
Main Results:
- This section details the methodology and planned analysis of the AMBUSH trial, as the results are not yet available from the provided abstract.
- The trial is designed to generate crucial data on the effectiveness of SHH pathway inhibition in a previously understudied adult/AYA MB population.
- Key outcome measures will likely include progression-free survival, overall survival, and response rates within the SHH-MB cohort.
Conclusions:
- The AMBUSH trial represents a significant step towards personalized treatment for adult and AYA medulloblastoma, particularly for the SHH molecular subgroup.
- Findings from this trial are expected to inform future treatment guidelines for this rare cancer in older patient populations.
- Targeting the SHH pathway with inhibitors offers a promising therapeutic strategy for a substantial subset of adult/AYA MB patients.
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