Young children with medulloblastoma: important open questions and the high-risk dilemma

Medulloblastoma in children with Fanconi anemia: Association with FA-D1/FA-N, SHH type and poor survival independent of treatment strategies

BACKGROUND

The outcome of children with medulloblastoma (MB) and Fanconi Anemia (FA), an inherited DNA repair deficiency, has not been described systematically. Treatment is complicated by high vulnerability to treatment-associated side effects, yet structured data are lacking. This study aims to give a comprehensive overview of clinical and molecular characteristics of pediatric FA MB patients.

METHODS

Clinical data including detailed information on the treatment and toxicities of 6 previously unreported FA MB patients were supplemented with data of 16 published cases.

RESULTS

We identified 22 cases of children with FA and MB with clinical data available. All MBs with subgroup reporting were SHH-activated (n = 9), confirmed by methylation profiling in 5 patients. FA MB patients exclusively belonged to complementation groups FA-D1 (n = 16) or FA-N (n = 3). Patients were treated with postoperative chemotherapy only (50%) or radiotherapy (RT) ± chemotherapy (27%). Of 23% did not receive adjuvant therapy. Excessive treatment-related toxicities were frequent. Severe hematological toxicity occurred in 91% of patients treated with alkylating chemotherapy, while non-alkylating agents and RT were less toxic. Median overall survival (OS) was 1 year (95%CI: 0.3-1.8). 1-year-progression-free-survival (PFS) was 26.3% ± 10.1% and 1-year-OS was 42.1% ± 11.3%. Adjuvant therapy prolonged survival (1y-OS/1y-PFS 0%/0% without adjuvant therapy vs. 53.3% ± 12.9%/33.3 ± 12.2% with adjuvant therapy, P = .006/P = .086).

CONCLUSIONS

MB in FA patients is strongly associated with SHH activation and FA-D1/FA-N. Despite the dismal prognosis, adjuvant therapy may prolong survival. Non-alkylating chemotherapy and RT are feasible in selected patients with careful monitoring of toxicities and dose adjustments. Curative therapy for FA MB-SHH remains an unmet medical need.

How do we approach the management of medulloblastoma in young children?

Therapeutic strategies avoiding craniospinal irradiation were developed for young children with medulloblastoma to improve survival while protecting the neurocognitive outcomes of these vulnerable patients. These strategies most commonly rely on high-dose chemotherapy with stem cell rescue or conventional chemotherapy combined with intraventricular chemotherapy or conventional chemotherapy with adjuvant focal irradiation. Over the past decade, our growing understanding of the molecular landscape of medulloblastoma has transformed how we risk stratify and allocate treatment in this young age group. We present the results of the most recent approaches and clinical trials for medulloblastoma of early childhood, according to the different molecular subgroups. Overall, young children with sonic hedgehog medulloblastoma treated with intensive adjuvant chemotherapy achieve excellent survival and can safely be spared from radiotherapy. For patients with group 3 and 4 medulloblastomas, the interplay between molecular alterations and treatment intensity still needs to be further delineated. While recent clinical trials point toward more encouraging survival figure for a sizeable number of them, patients identified with very high-risk feature desperately needs innovative therapies.