Pediatric Medulloblastoma

Medulloblastoma is a heterogeneous disease. Recent advances in understanding the molecular characteristics of medulloblastoma cells allowed for sub-typing based on abnormalities seen at the molecular level. These subgroups are defined by their unique clinical behavior and outcomes.

The WNT-subgroup, which accounts for 10% of medulloblastoma cases in children, is characterized by aberrant activation of the Wingless (WNT) signaling pathway. The most frequently mutated genes in WNT medulloblastoma are CTNNB1 and TP53.

The SHH-subgroup accounts for 30% of medulloblastoma cases in children and is characterized by aberrant activation of the Sonic hedgehog (SHH) signaling pathway. The most frequently mutated genes in SHH medulloblastoma are PTCH1, SMO, SUFU, GLI1 and TP53.

Groups 3 and 4 which accounts for 25 and 35% of medulloblastoma cases respectively, lack involvement of any clearly defined signaling pathway. Common genetic alterations involves MYC, OTX2 and SMARCA4 in group 3, and KDM6A and MYCN in group4.

The most recent WHO classification of medulloblastoma is as follows[2] :

• Medulloblastoma, genetically defined.

  • Medulloblastoma, WNT-activated.
  • Medulloblastoma, SHH-activated and TP53-mutant.
  • Medulloblastoma, SHH-activated and TP53-wildtype.
  • Medulloblastoma, non-WNT/non-SHH.
    • Medulloblastoma, group 3.
    • Medulloblastoma, group 4.
• Medulloblastoma, histologically defined.

  • Medulloblastoma, classic.
  • Medulloblastoma, desmoplastic/nodular.
  • Medulloblastoma with extensive nodularity.
  • Medulloblastoma, large cell/anaplastic.
• Medulloblastoma, NOS.

Environmental causes

Epidemiological studies investigating parental occupational exposures, environmental exposures, and maternal nutritional intake have not proven a direct link between such factors and the development of childhood brain tumors.

Familial and heritable cancer predisposition syndromes associated with medulloblastoma

In one study, 5 of 37 (13.5%) patients with medulloblastoma were found to have germline mutations in one of the known cancer predisposing genes.[3]

Syndromes known to be associated with medulloblastoma include the following:

• Turcot syndrome (related to germline mutations in APC)
• Rubinstein-Taybi syndrome (related to germline mutations in CREBBP)
• Gorlin syndrome (associated with germline PTCH1 and SUFU mutations)
• Li-Fraumeni syndrome (associated with germline mutations in TP53)
• Fanconi anemia

United States statistics

Approximately 250 new patients are diagnosed annually.

International statistics

Exact figures are unknown. In general, brain tumors occur at a rate of 2.5-4 per 100,000 at-risk children per year. Of these, approximately 18% are medulloblastoma.

Race-, sex-, and age-related demographics

No racial predisposition is noted. Data from the Surveillance, Epidemiology, and End Results (SEER) program showed that patients aged 0-14 years in the United States have an incidence rate per million population of 5.7 in whites and 5 in blacks.[4]

US incidence per 1 million population for patients aged 0-14 years is 6.1 for boys and 4.5 for girls.

Peak age of incidence is during the first decade of life. Approximately 80% of patients are diagnosed in the first 15 years of life.

Prognostic factors include the following:

1. Age at diagnosis
2. Metastatic stage (M stage) at time of presentation
3. Extent of surgical resection
4. Histology
5. Molecular subtype

The specific risk groups based on clinical findings and morphology are defined as follows:

• Average-risk disease: This risk group is defined as patients older than 3 years who have no evidence of dissemination and with less than 1.5 cm ² of residual tumor postoperatively. The 5-year survival rate for this group is currently 85%.
• High-risk disease: This risk group is defined as patients older than 3 years with evidence of metastatic disease, with more than 1.5 cm ² of residual tumor postoperatively and/or large cell/anaplastic histology. Large cell/anaplastic histology is commonly associated with unfavorable molecular changes like MYC amplification and predicts poor outcome. The 5-year survival rate for this group is currently 30-60%.
• Infants: This group is defined as patients younger than 3 years. The 5-year survival rate is 30-70% depending on clinical and molecular risk factors; patients with metastatic disease do considerably worse while those with WNT-activated or SHH-activated medulloblastoma are much more likely to survive.

The following genetically defined subgroups have variable outcomes:

• Patients with WNT-activated medulloblastoma have excellent prognosis with more than 90% long-term survival. 
• Patients younger than 4 years with SHH-activated medulloblastoma do well with 5-year event free survival of 85% when treated with surgery and chemotherapy alone. Children older than 4 years with SHH-activated medulloblastoma without TP53 mutation do fairly well with 5-year event free survival of 60%. However, patients with SHH-subgroup with TP53 mutation do significantly worse.
• Patients with Group 3 have the worst outcome with close to 50% long-term survival.
• Patients with Group 4 have close to 75% long-term survival.

Morbidity/mortality

Clinical risk group stratification is continuing to evolve but is currently based on four principal features including age, extent of postoperative residual disease, and the metastasis stage.

Molecular subtype provides significant information regarding tumor behavior and response to treatment. Patients with WNT subtype for example have an excellent prognosis, while patients with MYC or MYCN amplification do poorly.  

Despite successful treatment, a significant number of patients have neurocognitive, neurologic and endocrinologic deficits. Many children subsequently develop learning difficulties that require individualized educational programs. Biochemical growth deficiency is observed in 70-80% of patients, and some degree of growth impairment is present in well over half of patients after treatment. Thyroid and gonadotropin hormonal deficiency may also occur. Craniospinal radiation, a mainstay of treatment, has been implicated as a major cause of these deficits.

Complications

The following complications can be classified based on their etiology:

Disease-related

• Temporary or permanent neurologic impairment, particularly cerebellar dysfunction

• Headaches

Surgical complications

• Posterior fossa syndrome (mutism, cerebellar dysfunction, cranial nerve palsy, and hemiparesis; generally temporary)

• Bleeding

• Shunt malfunction or infection

Radiation-induced

• Nausea/vomiting, anorexia

• Other GI toxicity (e.g. mouth sores, diarrhea)

• Cytopenias (from irradiation of vertebral bodies, which encompasses 40% of bone marrow) including lymphopenia

• Neurocognitive impairment

• Somnolence syndrome (transient sleepiness, typically occurs 4 to 6 weeks from start of radiation)

• Radiation necrosis, a potential long-term (may develop months or even years after) sequela resulting in edema from death of tumor cells or tissue from radiation exposure

• Intratumoral hemorrhage

• Ototoxicity

• Hypopituitarism (e.g. hypothyroidism, growth hormone deficiency)

• Secondary malignancies to radiation field areas

Chemotherapy-related

• Anemia causing headaches and fatigue

• Thrombocytopenia and risk for bleeding

• Neutropenia and increased risk for infections

• Mucositis (can be especially severe with thiotepa)

• Constipation (vincristine-related)

• Organ toxicity

  • Hepatotoxicity

  • Nephrotoxicity, ototoxicity with cisplatin/carboplatin

  • Hemorrhagic cystitis with cyclophosphamide

  • Neurotoxicity with vincristine

• Secondary leukemia from alkylator therapy

• Metabolic syndrome (diabetes, hyperlipidemia and heart disease) in stem cell transplant recipients

• Infertility

Patients and family members should be instructed about the care of the central venous catheter.

Patients should be instructed about measures to minimize infections (eg, proper handwashing, central line care, avoiding sick contacts) and seeking immediate medical attention for fevers or other signs of infection that manifest during therapy.

The majority of medulloblastoma tumors arise in the 4th ventricle and cause obstructive hydrocephalus. About 70-90% of patients with medulloblastomas present with a history of headaches, emesis, and lethargy; these symptoms are generally intermittent and subtle at first. Duration of symptoms for 3 months or more before diagnosis is common.

Increased intracranial pressure (ICP)

Early symptoms are secondary to increased ICP. The classic triad consists of morning headaches, vomiting, and lethargy. Headache consists of head pain present upon arising that is relieved by vomiting and gradually lessens during the day. Cushing triad (ie, hypertension, bradycardia, and hypoventilation), an uncommon finding in children with increased intracranial pressure, usually indicates impending herniation.

Initial signs of increased ICP are usually subacute, nonspecific, and nonlocalizing.

School-aged children may complain of vague intermittent headaches and fatigue. They may demonstrate declining academic performance and personality changes.

Infants may present with irritability, anorexia, and developmental delay.

Cerebellar dysfunction

With increasing tumor size and invasion into the surrounding brain tissue, more characteristic symptoms appear. One symptom is progressively worsening ataxia involving the lower extremities, often with relative sparing of the trunk and upper extremities.

Brain stem deficits

Tumor infiltration of the brain stem or increased ICP may result in diplopia and multiple other cranial nerve findings, such as facial weakness, tinnitus, hearing loss, head tilt, and stiff neck.

Metastatic disease

Uncommonly, patients may present with back pain or leg weakness secondary to spinal metastasis.

The earliest signs are nonlocalized and caused by increased ICP. Later signs are generally due to tumor invasion of the surrounding tissue.

Increased ICP

Funduscopic evaluation reveals papilledema or optic pallor in infants.

Palsy of cranial nerve VI resulting in the inability to abduct one or both eyes is common.

Infants may have the "setting sun" sign. This is demonstrated by impaired upgaze and seemingly forced downward deviation of the eyes.

Measurement of head circumference in infants with open cranial sutures also may reveal macrocephaly.

Cerebellar findings

Localized deficits in truncal steadiness, upper extremity coordination, and gait are common.

Brain stem findings

Invasion into the brain stem may cause loss of conjugate gaze (gaze palsy) or the inability to adduct one eye on attempted lateral gaze. This is observed most commonly in combination with deficits of cranial nerves V, VII, and IX.

Invasion into the cerebellopontine angle results in facial weakness and hearing loss, often with associated unilateral cerebellar deficits.

The routine pretreatment laboratory evaluation for medulloblastoma includes a complete blood cell (CBC) count, electrolytes, liver, and renal function tests. Baseline thyroid function studies and viral titers are also recommended.

Diagnosis is usually made by magnetic resonance imaging (MRI) or computed tomography (CT). 

CT scanning

CT scan of the brain is commonly used during initial evaluation of patients with neurologic symptoms. In patients with medulloblastoma, CT scan of the head with and without contrast usually shows a solid mass in the 4th ventricle with prominent hydrocephalus in most patients. The vast majority (95%) of medulloblastoma are contrast-enhancing.

MRI

Head and spinal MRI with and without gadolinium should be performed in all patients with CT or clinical findings consistent with medulloblastoma. MRI better demonstrates the anatomic origin and extent of tumor (see the image below). More than 90% of medulloblastoma tumors enhance with contrast. Contrast is essential to detect CSF dissemination.

Preoperative and postoperative MRI is required for detection and measurement of residual disease following surgical resection. Postoperative MRI evaluation should be performed within 72 hours of surgery to delineate residual tumor from the postsurgical inflammatory changes that are visualized on MRI at this time.

Spinal MRI is the most sensitive method available for detection of spinal cord metastasis.

MRI showing a medulloblastoma of the cerebellum.

Bone scanning

Because medulloblastoma can metastasize outside the CNS, especially to bone, a bone scan with plain film correlation may be useful in symptomatic patients.

A baseline hearing test (audiography or brainstem auditory-evoked response [BAER]) is recommended because of the potential toxicity from radiation and chemotherapy.

Some investigational treatment protocols may require additional tests, such as echocardiography, pulmonary function tests, or other more specific tests, for the purposes of monitoring treatment-related toxicity.

Lumbar puncture

CSF cytologic examination is useful for the detection of microscopic leptomeningeal tumor dissemination. However, neither clinical symptoms nor negative CSF cytologic findings can be relied on to indicate the presence of nodular spinal cord disease. As many as 50% of patients with positive spine MRI studies are asymptomatic and have negative cytologic results.

Funduscopic examination (or CT or MRI) must be performed before lumbar puncture (LP) to rule out the presence of hydrocephalus.

In known cases of medulloblastoma, LP generally is deferred until 2 weeks postoperation to avoid false-positive results from the presence of tumor cells that have disseminated as a result of surgery.

Bone marrow aspirate and biopsy

Medulloblastoma rarely metastasizes to bone marrow.

These tests should be reserved for patients who demonstrate abnormal peripheral blood findings that have no clear etiology.

Medulloblastomas are undifferentiated embryonal neuroepithelial tumors of the cerebellum. They are highly cellular, soft, and friable tumors composed of cells with deeply basophilic nuclei of variable size and shape, little discernible cytoplasm, and often abundant mitoses (see the image below).

This section displays a typical medulloblastoma, composed of undifferentiated cells with deeply basophilic nuclei of variable size and shape and little discernible cytoplasm.

These characteristics give the microscopic appearance of a small, round, blue cell tumor. Morphologically identical tumors arising in the pineal region are termed pineoblastomas, and those arising in other CNS locations are called embryonal tumors, NOS.

Homer-Wright rosettes (ringlike accumulations of tumor cell nuclei around a neuropil-containing or fibrillary core) and pseudorosettes are variably present (see the image below).

Section displaying Homer-Wright rosettes and pseudorosettes of a medulloblastoma.

These tumors express neuronal and neuroendocrine markers, including synaptophysin and neurofilament proteins.

There are four major histological variants: classic, desmoplastic/nodular, large cell/anaplastic and medulloblastoma with extensive nodularity.

Staging is based on the extent of tumor at the time of diagnosis and the degree of surgical resection. Complete staging requires pre- and postoperative MRI of the entire brain and spine, postoperative MRI of the tumor site, and CSF analysis. Table 1 summarizes the modified Chang staging system for posterior-fossa medulloblastoma.

Table. (Open Table in a new window)

Following upfront maximal safe surgical resection, standard of care approach for medulloblastoma is dependent on risk stratification and generally consists of chemotherapy and radiotherapy. New treatment approaches are being developed in an attempt to reduce long-term toxicity of therapy and include reduction of the total dose or volume of radiotherapy, use of less neurotoxic chemotherapeutic agents and newer targeted therapeutic agents, and use of high dose chemotherapy with autologous stem cell rescue in lieu of craniospinal irradiation (CSI).

Although there is insufficient evidence to routinely recommend the use of proton therapy, for younger children with medulloblastoma, strong consideration should be given for proton-beam radiotherapy when available.  Compared to conventional radiotherapy, proton-beam therapy provides similar efficacy but offers the advantage of minimizing the risk of long term side effects including but not limited to ototoxicity, cardiopulmonary toxicity and secondary malignancies.[5]

Studies that incorporate molecular profiling to guide adjuvant therapy are underway.

Radiation therapy

Radiation strategies can be divided into local control and treatment of micrometastatic disease with craniospinal irradiation.  Historically, the entirety of the cerebellum (posterior fossa) was radiated.  Increasingly, the approach of more precise targeting of the tumor bed with an appropriate margin is being done.

Average-risk disease

The current recommendation is 23.4 Gy to the craniospinal axis, followed by a boost of 30.6 Gy to the primary tumor site.  In general, start of radiation should be timed for no later than 4 weeks from surgery to maximize clinical outcomes.

Reducing the amount of craniospinal radiation in an attempt to decrease morbidity without jeopardizing survival appears to be successful in this group. In a report by the International Society of Pediatric Oncology, children with average-risk medulloblastoma randomly received either the standard 36 Gy or a reduced dose of 24 Gy to the neuraxis.[6] It was found that no statistical difference in progression-free survival rates was demonstrated between the groups as long as the initiation of radiotherapy was not delayed by the administration of chemotherapy before radiation.

In the largest trial conducted for average-risk medulloblastoma by the Children's Oncology Group (COG), survival rates following reduced radiation therapy boost volumes were comparable to standard treatment volumes for the primary tumor site but lower CSI doses were associated with higher relapse rates and worse survival outcomes.  In this study, patients less than 8 years of age were randomized to receive 18 Gy vs. 23.4 Gy whereas all patients were randomized to either local boost versus radiation to the entire posterior fossa.[7]

Studies to determine the feasibility of avoiding radiation therapy altogether in WNT-activated medulloblastoma, a subgroup with excellent prognosis, are ongoing.

High-risk disease

The current recommendation is 36 Gy to the craniospinal axis, followed by a boost of 19.8 Gy to the primary tumor site and an additional 19.8 Gy to focal metastatic sites. In general, start of radiation should be timed for no later than 4 weeks from surgery to maximize clinical outcomes.

Infants (< 3 years of age)

Radiation therapy for patients younger than 3 years, the poorest risk group, is generally avoided because of its deleterious effects on intellectual development especially in this age group.  Previous attempts to decrease CSI dose and maintain outcomes in this age group were unsuccessful.  In lieu of this, in an effort to delay or omit radiation, current protocols utilize high dose chemotherapy approaches.

Relapse/Recurrence

There remains no standard approach in the treatment of relapsed medulloblastoma. The prognosis for relapsed medulloblastoma is dismal, especially in those who have previously received radiation. Treatment approach is primarily based on whether the child has had craniospinal radiation as part of initial therapy. Re-irradiation is often not performed due to concerns surrounding cumulative CNS toxicity and unknown efficacy.  If a patient has had prior craniospinal radiation, a small boost of radiation can still be considered.

Chemotherapy

Cytotoxic chemotherapy may be used in the initial treatment (in infants), as maintenance therapy (for average and high-risk disease) or for disease recurrence. In patients less than 3 years of age, incorporation of high dose chemotherapy strategies may delay or obviate the need for radiation therapy.

To date, there exists only a handful of open clinical trials that incorporate molecular risk stratification to help guide therapy.

Average-risk disease

Standard therapy post-radiation is with the use of cisplatin-based regimens. Many contemporary chemotherapy protocols use a combination of cisplatin, vincristine, lomustine (CCNU) and cyclophosphamide as maintenance therapy for approximately one year following radiation therapy.

Group 2/SHH-activated medulloblastomas are characterized by mutations in smoothened SMO, which is upstream of SHH.  Vismodegib, an SMO inhibitor, has promising efficacy in patients who harbor upstream SHH-pathway mutations (ie, SMO and PTCH1 mutations)

High-risk disease

As in average risk medulloblastoma, following induction therapy with radiation therapy, the most effective chemotherapy agents utilized are cisplatin, vincristine, lomustine (CCNU) and cyclophosphamide.  The use of daily carboplatin (in addition to weekly vincristine) as a radiosensitizing agent is currently being studied in high risk medulloblastoma.

Risk adapted radiotherapy followed by a shortened schedule of four consecutive high dose cyclophosphamide-based chemotherapy with autologous stem cell rescue has been shown to improve outcome of patients with high risk medulloblastoma.[8]  

Group 3 and 4 patients generally fare poorer than group 1/WNT and group 2/SHH cases. As such, St. Jude is investigating the addition of gemcitabine, a pyrimidine nucleoside analogue, and pemetrexed, a folate antimetabolite, to group 3 and 4 medulloblastoma patients based on promising pre-clinical data.[9]

Infants

Intensive chemotherapy with stem cell support has shown promise in recurrent and infant medulloblastoma cases. Dose intensive chemotherapy strategies incorporate up to five cycles of high dose methotrexate-based regimens followed by high dose chemotherapy (up to three courses using carboplatin, thiotepa with or without etoposide) with autologous stem cell rescue. Stem cells are typically harvested following the first cycle of induction chemotherapy and frozen for later use. 

Recurrence

There is no standard chemotherapy approach for relapsed medulloblastoma. Overall outcomes are poor and median overall survival following relapse is less than one year. The combination of bevacizumab and irinotecan, with or without temozolomide, can produce objective responses with minimal toxicity in recurrent medulloblastoma cases. High dose chemotherapy with autologous stem cell rescue has shown potential benefit in patients who are able to achieve minimal residual disease following salvage chemotherapy but carry significant morbidity. Alternatively, metronomic chemotherapy, an approach where low daily doses of drug are used to reduce tumor angiogenesis and promote cancer apoptosis, with or without the addition of intrathecal chemotherapy, has also shown promise with few reports of long term survivors.

The goal of surgery is to resect as much of the tumor as safely as possible and to reduce the pressure inside the brain caused by blockage of cerebrospinal fluid (CSF) outflow.

Suboccipital craniotomy

Because the tumor is often friable, gentle suction is used. Microdissection is then used to remove adherent portions. Modern neurosurgical techniques permit complete or near-complete resection with little or no significant increase in morbidity and mortality rates compared with more conservative surgery.

Because surgical estimates of the extent of resection may not be reliable, postoperative MRI evaluation for residual disease is required within 72 hours of surgery the procedure.

As many as 40% of patients have some degree of new neurologic dysfunction postoperatively. One ill-defined syndrome is posterior fossa syndrome, characterized by mutism, cerebellar dysfunction, supranuclear cranial nerve palsy, and hemiparesis that occurs 12-48 hours after surgery. Symptoms generally resolve within weeks to months from surgery with the help of speech, occupational and physical therapy. However, as many as 50% of patients can experience long-term residual deficits.

Ventriculoperitoneal shunt

Treatment of hydrocephalus is almost always needed in medulloblastoma patients. Approximately 50% of cases require placement of a ventriculoperitoneal shunt at the time of operation (or shortly thereafter) because of unresolving obstructive hydrocephaly. Alternatively, endoscopic third ventriculostomy is increasingly used to avoid the placement of a permanent ventricular shunt; this approach can be successful in as much as a third of patients.

Central venous catheter placement

Surgically placed catheter inserted into a large deep vein and used to obtain blood tests and administer chemotherapy.  Generally, an implanted port is placed on one side of the chest.  In younger patients or those requiring high dose chemotherapy and autologous stem cell transplantation, a tunneled Broviac line may be placed instead.

Ommaya reservoir

Some infant brain tumor protocols combine systemic chemotherapy with intrathecal/intraventricular chemotherapy. Placement of an Ommaya reservoir facilitates repetitive administration of drugs into the CSF and ensures more reliable drug delivery and distribution.

In North America, intraventricular administration of chemotherapy requiring Ommaya placement is primarily restricted to salvage protocols in relapsed cases.

As a direct result of the tumor and/or therapy, many patients are referred to occupational, physical, hearing, and speech therapists for rehabilitation of common neurologic dysfunction. Neuro-ophthalmologists may also be consulted after successful treatment to evaluate persistent gaze palsies that may affect visual development.

Team members for the care of all patients should include specialists from each of the following:

• Neurosurgery

• Pediatric oncology (Neuro-oncology when available)

• Radiation oncology

• Neuroradiology

• Neurology

• Psychology

• Endocrinology

• Rehab Medicine

• Ophthalmology (Neuro-ophthalmology when available)

Diet

No specific dietary restrictions or requirements are indicated.

Patients who develop severe anorexia or weight loss as a result of therapy may need supplemental nutrition to maintain daily requirements. Most patients can tolerate enteral supplementation, but may require nasogastric/nasojejunal (NG/NJ) tube placement while some may need parenteral support.  Less commonly, surgery may be needed for gastrostomy tube (G-tube) placement.

Activity

Most patients have no restrictions on activity other than limitations from neurologic deficits caused by the tumor and treatment.

Patients with central lines and/or ventriculoperitoneal shunts may be restricted from performing high-impact sports (eg, diving, wrestling).

School performance needs to be carefully monitored and depending on limitations from neurologic deficits, may require added support at school.

Specific treatment regimens are dictated by the most current therapeutic protocols available for the treatment of medulloblastoma. In North America, the standard of care generally follows treatment regimens from the Children’s Oncology Group.

In the United Kingdom, the Children’s Brain Tumour Research Centre produced the Diagnosis of Brain Tumours in Children guideline, which was accredited by the National Institute for Health and Care Excellence. A summary of the guideline for healthcare professionals covers diagnosis, presenting symptoms of brain tumors in children by subspecialty, and when to refer for further assessment, imaging, or treatment.[10]

Historically, the most active drugs have been DNA alkylators. These agents cause DNA damage and disrupt DNA replication. Most chemotherapy is given in the inpatient setting.  Standard of care regimens in North America incorporate the below chemotherapeutic agents:

• Vincristine
• Lomustine
• Cisplatin
• Cyclophosphamide

Infant protocols generally incorporate the addition of the following chemotherapeutic agents:

• Etoposide
• Methotrexate (high dose)

Different high dose chemotherapy regimens have been used previously.  In North America, the most commonly used regimens are either a single transplant with carboplatin, thiotepa and etoposide OR triple tandem transplantation with smaller doses of carboplatin and thiotepa.  The currently open Head Start IV multi-institutional trial seeks to address the use of a single versus triple tandem regimen.

Vincristine (Vincasar PFS)

Vincristine, a plant-derived vinca alkaloid used during radiotherapy and in combination with other chemotherapeutic agents.  Acts as a mitotic inhibitor by binding tubulin.  Common adverse effects include peripheral motor and sensorineural neurotoxicity and constipation.  This agent by itself does not cause myelosuppression or nausea/vomiting.

Lomustine (Gleostine)

Lomustine (CCNU), a nitrogen mustard and DNA alkylator used in combination with other chemotherapeutic agents.  Acts by crosslinking DNA resulting in damage to the DNA templation and inhibits DNA replication.  Common adverse effects include myelosuppression as well as GI toxicity.

Cisplatin

Cisplatin, a heavy metal platinum derivative used in combination with other chemotherapeutic agents.  It exerts its cytotoxic effect by platination of DNA.  Acts similarly to alkylating agents by crosslinking DNA and inhibiting DNA replication.  Common adverse effects include myelosuppression, acute and delayed onset nausea and vomiting, hair loss, ototoxicity and nephrotoxicity and electrolyte disturbance (e.g. hypomagnesemia).

Cyclophosphamide

Cyclophosphamide, a phosphoramide mustard and DNA alkylator used in combination with other chemotherapeutic agents.  Common adverse effects include myelosuppression, nausea/vomiting, hair loss, and hemorrhagic cystitis.

Methotrexate (Xatmep, Trexall, Rasuvo, Otrexup)

Methotrexate, a folate antimetabolite, is given at high doses to facilitate CSF penetration.  Common adverse effects include nausea/vomiting, myelosuppression, mucositis, and nephrotoxicity.

Etoposide (Toposar)

Etoposide (VP-16), a semisynthetic plant derivative of podophyllotoxin.  It is a topoisomerase II enzyme inhibitor and forms a ternary complex with DNA causing DNA strands to break.  Common adverse effects include infusion reactions, low blood pressure, hair loss, metallic taste, and myelosuppression.

Further inpatient care

Admit patients with medulloblastoma for specific chemotherapy and for complications (eg, neutropenic fever) as a result of therapy.

Further outpatient care

Radiotherapy

Daily outpatient radiotherapy (usual dose fractions of 180 cGy/day) is performed for approximately 6 weeks.

Physical and neurologic examination

Careful monitoring of response and treatment-associated side effects is performed weekly during radiotherapy and at least every 2 weeks during chemotherapy.

Reevaluation immediately before each cycle of chemotherapy is necessary to document resolution of previous treatment-related toxicities.

Following the completion of therapy, assessments are conducted every 3 months for the first 12-18 months, every 6 months for the next 2 years, and then annually, provided no complications have occurred.

Imaging studies

To have an objective measurement of tumor response to therapy, MRI with contrast of the head and spine is performed at the completion of radiotherapy, after every 2-3 cycles of chemotherapy, and at the end of therapy.

Following the completion of therapy, follow up brain and spine imaging studies are conducted every 3 months for the first 12-18 months, every 6 months for the next 2 years, and then annually, provided no complications have occurred.  Simultaneous spine imaging is performed

Laboratory studies

Weekly CBC counts are necessary during the initial phase of radiation therapy.  Every attempt should be made to maintain the patient’s hemoglobin at or above 10 mg/dL to improve radiation outcomes.

During chemotherapy, once to twice weekly CBC counts may be necessary in anticipation of possible need for red cell and/or platelet transfusions as well as need from granulocyte colony stimulating factor (G-CSF) support to abrogate neutropenic fever admissions.  Other labs, namely, liver function studies, electrolytes, renal function, and a hearing test are to be obtained before each cycle of chemotherapy and again at the end of treatment.

A baseline endocrinologic and neuropsychologic evaluation should be performed at the completion of therapy and annually thereafter.

Additional tests for the purposes of monitoring specific investigational protocol treatment-related toxicity (eg, echocardiogram, pulmonary function tests, etc.) may be required according to protocol guidelines.

Transfer

Transfer to centers that can provide appropriate MRI imaging studies, neurosurgical intervention, radiotherapy (particularly proton beam therapy), and chemotherapy may be necessary.

Inpatient medications are dictated by the most current chemotherapeutic protocols available for the treatment of medulloblastoma. See previous section on medications.

All regimens require the concomitant use of anti-emetic agents.  Special care should be taken into maximizing the use of anti-emetic agents (e.g. addition of aprepitant) for cisplatin, a highly pro-emetic agent.

Granulocyte colony stimulating factor (GCSF) following chemotherapy may be used in treatment regimens expected to cause marked neutropenia.  Intravenous gammaglobulin (IVIG) replacement to keep IgG levels >400 mg/dL is generally use to help prevent infections in infants.  It may also be used for patients whose treatment is complicated with viral infections.

Because of the immunosuppressive effects of chemotherapy, trimethoprim sulfamethoxazole are commonly prescribed for prophylaxis against Pneumocystis jiroveci pneumonia until 3-6 months after completion of chemotherapy.

Infants, especially those anticipated to receive high dose chemotherapy and autologous stem cell transplantation, also benefit from additional antifungal prophylaxis with fluconazole (to prevent systemic candidiasis) and palivizumab, a respiratory syncytial virus (RSV) specific passive antibody administered as an injectable medication monthly during the cold season.  Autologous stem cell transplantation recipients will also need re-immunized starting 6 months post-transplant.