Adult Medulloblastoma Treatment Guidelines

Introduction to Treatment Approach

The primary treatment approach for adult medulloblastoma is maximal safe surgical resection followed by risk-stratified craniospinal irradiation (CSI) with concurrent and adjuvant chemotherapy, with treatment intensity determined by molecular subtype, extent of resection, and metastatic status 1

Adults with medulloblastoma must be referred to specialized centers or "centers of excellence" at diagnosis or recurrence, as treatment at academic high-volume centers is associated with longer survival rates, reduced 30-day readmission (22% decrease), and lower 90-day mortality (16% decrease) 2, 3
These centers should provide multidisciplinary expertise including neurosurgery, neuropathology, radiation oncology, neuro-oncology, advanced molecular testing capabilities, regular tumor boards, access to proton therapy, and clinical trial programs 4

Pursue maximal safe surgical resection aiming for gross total resection (GTR) while minimizing neurologic deficits, as extent of resection correlates with survival 1
Obtain sufficient tissue at initial surgery for DNA methylation testing and molecular characterization, which is critical for risk stratification and treatment planning 4, 1

Routinely conduct DNA methylation testing for diagnosis and molecular subgrouping in all adult patients, as this is superior to immunohistochemistry for accurate classification 5, 1
Molecular subgroups have distinct prognoses: WNT-activated (>90% long-term survival), SHH-activated TP53-wild-type (intermediate prognosis), SHH-activated TP53-mutant (very poor prognosis), Group 3 (20-30% 5-year survival), and Group 4 (75-90% 5-year survival) 1

Initiate craniospinal irradiation within 30-42 days of tumor resection, as delays beyond this timeframe are associated with worse outcomes in pediatric studies, and similar principles likely apply to adults 6, 5, 7, 8

Average-risk patients (no metastases, residual tumor <1.5 cm²) should receive 23.4 Gy CSI with involved field boost to 54 Gy, plus concurrent weekly vincristine during radiotherapy 1
High-risk patients (metastatic disease or large residual tumor) should receive 36 Gy CSI with involved field boost to 54-55.8 Gy 1

Administer concurrent weekly vincristine during radiotherapy for all risk groups 1

Discuss contraception and fertility preservation before initiating therapy, given the young age of most adult patients and high risk of treatment-induced infertility 5, 2, 4
Evaluate patients at baseline and throughout treatment for endocrine dysfunction, vision and hearing deficits, and neurocognitive impairment 5, 2, 4

Use MRI with gadolinium contrast of brain and spine for surveillance, as this is superior to other modalities for detecting leptomeningeal dissemination 1
Include cerebrospinal fluid cytology, neurologic examination, and steroid use assessment in response evaluation 6, 7, 8

Strongly encourage enrollment in clinical trials or registries at diagnosis and recurrence, as information from every patient carries great value given the rarity of adult medulloblastoma (only ~140 new cases annually in patients ≥15 years in the United States) 9, 4

Recurrent medulloblastoma after first-line therapy occurs in approximately one-third of patients and carries survival rates <10% 1
For recurrence after 3-5 years, rebiopsy the tumor to distinguish between recurrent medulloblastoma and secondary malignancy, and to identify actionable molecular findings 1

Do not delay molecular testing or treatment initiation while awaiting results, as the 30-42 day window from resection to CSI is critical 5, 7, 8
Do not rely solely on immunohistochemistry for molecular classification, as DNA methylation is more accurate and IHC interpretation can be operator-dependent 5
Do not underestimate treatment toxicity in adults compared to children, as adults experience worse tolerance despite younger age 5
Do not use inadequate imaging protocols, as this is linked to worse event-free survival 6, 7, 8