Understanding Medulloblastoma Treatment in Young Children

The Challenges of Radiation Therapy

Radiation therapy is often avoided or postponed in young children diagnosed with medulloblastoma due to its potential adverse effects on long-term development. Consequently, treatment strategies prioritize chemotherapy. With a combination of surgery, chemotherapy, and radiotherapy, up to 80% of patients can attain long-term survival; however, this comes with significant toxic side effects. For children under three years old, radiotherapy is only utilized as a second-line salvage therapy due to its debilitating consequences.

Medulloblastoma Overview

Medulloblastoma, a type of brain cancer, stands as the leading cause of non-accidental fatalities in children and adolescents. Researchers have categorized medulloblastoma into four distinct molecular subgroups: WNT, sonic hedgehog (SHH), group 3, and group 4. Infants with this condition face poor survival rates, as about half of younger patients require salvage therapy or are left with terminal disease. Evidence suggests that different molecular subgroups of medulloblastoma respond variably to therapies that defer radiation.

Research Study on Risk-Adapted Approaches

In response to these challenges, a research team published a study in the Lancet Oncology aimed at determining whether risk-adapted treatment approaches could enhance survival rates for children with medulloblastoma. The study involved 81 children under five years old diagnosed with the condition, who were stratified into low, intermediate, and high-risk groups based on age and disease progression.

Treatment Protocol

All groups underwent a 16-week induction chemotherapy regimen that included methotrexate, vincristine, cisplatin, and cyclophosphamide. High-risk patients received an additional chemotherapy agent, vinblastine. Following this induction phase, a consolidation period lasted eight weeks. Low-risk patients continued with chemotherapy, intermediate-risk patients received focal radiation therapy, and high-risk patients were treated with chemotherapy combined with intravenous topotecan. After consolidation, patients entered a maintenance phase with cyclophosphamide, topotecan, and erlotinib for 24 weeks.

Study Outcomes

The primary endpoints of the study were event-free survival and the epigenetic profiles associated with progression-free survival. Results indicated that the event-free survival rate after five years was 55.3% in the low-risk group, 24.6% in the intermediate-risk group, and 16.7% in the high-risk group. Overall, the trial reported an event-free survival rate of 31.3% after five years. When analyzed by molecular subgroup, the SHH subgroup showed a progression-free survival rate of 51.1%, while group 3 and group 4 had rates of 8.3% and 13.3%, respectively.

Adverse Events and Conclusions

The most frequently reported adverse events included fever and infections, attributed to low neutrophil counts. Compared to previously reported studies on children with medulloblastoma, this risk-adapted approach did not yield improvements in overall event-free survival. However, specific molecular subtypes, especially within the SHH subgroup, demonstrated enhanced progression-free survival, indicating that certain subtypes of medulloblastoma may benefit from this stratified risk approach.

The authors of the study recommend further research to validate these findings across other clinical cohorts.

Reference

Robinson GW et al. Risk-adapted therapy for young children with medulloblastoma (SJYC07): therapeutic and molecular outcomes from a multicentre, phase 2 trial. Lancet Oncol. 2018 Jun;19(6):768-784. doi: 10.1016/S1470-2045(18)30204-3. Epub 2018 May 16.