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2021 Neurosurgeon Summary: How to treat medulloblastoma? Magnetic resonance imaging (MRI) is the preferred method for evaluation and follow-up of medulloblastoma.
Because the typical location of the tumor is in the posterior fossa, patients with medulloblastoma usually present with increased intracranial pressure, hydrocephalus, cerebellar signs with gait disorder or limb ataxia, and signs of leptomeningeal disease.
Due to the high incidence of SHH gene mutation tumors located in the cerebellar hemisphere, adults are more prone to limb ataxia. Neurocognitive impairment may also occur, mainly including impaired attention, visual perception, and language fluency.
Medulloblastoma has a tendency to spread to the subarachnoid space, and in a few cases, it spreads out of the nerves, such as lymph nodes, bone marrow, bones, etc. Lungs and liver, which may cause symptoms. Therefore, we recommend a thorough clinical and neurological examination when symptoms first appear.
Diagnosis of medulloblastoma
Magnetic Resonance Imaging (MRI) is the preferred method for evaluation and follow-up of medulloblastoma. The recommendations of magnetic resonance imaging have been defined by the Children’s Neurotumor Response Assessment Committee (RAPNO). Most medulloblastomas are unevenly enhanced and rarely have edema.
SHH medulloblastoma is often located in the cerebellar hemisphere, with more edema and limited diffusion. Since medulloblastoma can produce droplet metastasis and pia mater involvement, all patients should undergo spinal MRI before or after surgery if they develop clinical symptoms that may be related to spinal cord lesions before deciding on adjuvant therapy and during follow-up. Since medulloblastoma can show unusual MRI patterns, we recommend reviewing the MRI scan by an experienced neuroradiologist.
The picture shows the diagnosis and treatment of adult medulloblastoma (first-line treatment)
Staging and response assessment should include cerebrospinal fluid (CSF) cytology to detect pial dissemination, which should be performed before or after 14 days after surgery. A T-stage assessment should be performed because it may have prognostic value for adults. Stage M can be assessed, but its prognostic value for adults is not yet clear. Therefore, adult M0 and M1 patients are usually classified into the same prognosis group. Preoperative and postoperative neurological, neurocognitive, endocrine, auditory, visual, peripheral nerve and renal functions should be recorded. Psychological and social support should be provided to all patients.
How to treat adult medulloblastoma?
Definite tumor resection surgery should be used to relieve the common hydrocephalus caused by obstruction. If a clear operation cannot be performed immediately, an emergency outdoor drainage device should be placed. Vascular tumor edema should be reduced with corticosteroids before surgery. Preoperative management should be discussed in multiple disciplines on the brain tumor board. When feasible, all patients should undergo total total resection (GTR). When GTR is not feasible, the maximum safe resection should be performed to preserve the value of the functional area and leave residual tumors.
Postoperative craniocerebral spinal cord irradiation (CSI) has sufficient target volume to cover and preserve dangerous organs is mandatory. For photonic CSI, advanced technologies such as spiral radiation therapy or volume intensity modulated arc therapy (VMAT) should be used. Proton therapy is an option to reduce long-term side effects. The total dose is 36gy, the daily dose is 1.8 Gy (5 times/week) or 35.2 Gy, and the daily dose is 1.6 G (5 times/week). The CSI with a total dose reduction of 23.4 Gy has been determined in pediatric trials and will be evaluated in a prospective trial of adult M0-M1 disease. In addition to CSI, the local dose needs to be increased to the tumor bed, with a single dose increased from 1.8 Gy to 54.0 or 55.8 Gy. According to the pediatric protocol, we recommend starting radiation therapy within 28-42 days after surgery.
Medulloblastoma is a chemosensitive tumor. Adult patients with medulloblastoma should receive systemic treatment in addition to resection and radiotherapy, regardless of their risk category. Treatment recommendations are based on pediatric trials, retrospective analysis of adult cohorts in pediatric trials, and adult single-group prospective trials. The meta-analysis also showed that the effect of radiotherapy and chemotherapy is better than that of radiotherapy alone.
Packer chemotherapy regimen is based on lomustine, vincristine and cisplatin, and is a commonly used chemotherapy regimen for adults, at least in Europe. Adults seem to tolerate Packer chemotherapy worse than children. Therefore, we recommend reducing the frequency of vincristine administration to 2 times a week to avoid neurotoxicity, and reduce the maintenance period to 6 cycles of chemotherapy to reduce bone marrow toxicity. Substituting carboplatin for cisplatin to further prevent non-hematological side effects is a routine treatment for patients with cisplatin ototoxicity and nephrotoxicity, but it has not been studied as the main treatment for adults. Other cisplatin and etoposide-based regimens have also been used in adult patients.
Currently, there is no data to support high-dose chemotherapy combined with autologous stem cell transplantation to further improve the prognosis of adult medulloblastoma.
With the understanding of medulloblastoma subtypes, targeted therapy can be considered for individual cases and become part of recent prospective clinical trials. SMO inhibitors have been studied in several trials. Alternative chemotherapy regimens and targeted, immune and anti-angiogenic drugs have been studied in adults, always in small phase I or II trials, but have not yet been implemented as standard of care.
Prognosis observation and follow-up
In addition to clinical monitoring, MRI is also used to assess disease status, treatment response and follow-up. A three-month MRI scan during treatment is common practice and is recommended for all subgroups. After the active treatment phase is over, a head MRI follow-up plan for 3 to 6 months until the end of the 5th year, and 6 months to annual follow-up for up to 10 years may be feasible.
If the progress of the disease is suspected, short-term MRI confirmation should be performed. Clinical monitoring and follow-up should include at least clinical examination of endocrine function, assessment of vision, hearing, renal function, skin integrity, polyneuropathy and fertility, and consideration of social, psychological and fertility issues at each visit.
Recent studies have shown that medulloblastoma of the SHH subtype may have a higher tendency to relapse, so long-term follow-up is required.
(source:internet, reference only)