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Treatment of brain tumors in children
Last reviewed: 19.10.2021
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Surgical treatment of brain tumors in children
The standard and key method of treating CNS tumors is surgical removal. Over the past three decades, the survival of patients with CNS tumors has improved significantly due to the emergence of modern diagnostic methods (widespread magnetic resonance therapy with contrast enhancement), the improvement of neurosurgical techniques, neuroanesthesiology and resuscitation, and the improvement of accompanying therapy.
The leading role in the treatment of patients with brain tumors is played by neurosurgery. The operation allows to remove the tumor as much as possible and solve problems related to the mass effect (symptoms of intracranial hypertension and neurological deficit), that is, to eliminate the immediate threat to the life of the patient, and also to obtain material for determining the histological type of the tumor. Of particular importance is the macroscopically complete removal of the tumor, since the results of treatment of patients with totally removed neoplasm are better than the results of treatment of patients with a large residual tumor. Completeness of tumor removal is determined on the basis of the operation protocol and comparison of CT and MRI data prior to surgery and 24-72 hours after its completion.
Stereotactic biopsy is indicated for inoperable tumors in order to establish a histological type of neoplasm.
Radiation therapy of brain tumors in children
Radiation therapy is another important component of treating children with brain tumors. The determination of the optimal dose and irradiation fields depends on the size and location of the tumor, as well as on its expected spread. Total irradiation of the central nervous system is used at a high probability of spreading a tumor with a current of CSF.
In most tumors, the dose of radiation is determined by the need for tumor control and tolerance of normal brain tissue. Tolerance depends on a number of factors, including anatomical location (brainstem and spotalamus are most sensitive to irradiation), radiation doses and the child's age. Doses of 54 Gy, 45 Gy and 35 Gy, assigned daily 5 days a week are fractionally (from 1.6 to 1.8 Gy for local fields of the brain and spinal cord, respectively), are used in children older than 3 years, that is, with almost complete development of the brain. In young children, such doses can cause damage to nerve cells, delayed mental and physical development. That is why radiation therapy for children under 3 years old is not carried out.
Polychio-therapy of brain tumors in children
Polychemotherapy plays an important role in the complex treatment of brain tumors in children. Thanks to its use over the past 20 years, the results of treatment have improved significantly. It is especially relevant for certain histological types of tumors in young children, which it is desirable to postpone or exclude radiotherapy, as well as in inoperable neoplasms and metastasis.
For a long time, the use of systemic chemotherapy for brain tumors was considered inexpedient and ineffective. Among the reasons for this point of view, the presence of the blood-brain barrier was the first place. The blood-brain barrier slows the penetration of high molecular weight water-soluble drugs from the blood into the brain tissue, whereas low-molecular fat-soluble substances easily overcome it. In fact, the blood-brain barrier is not a serious obstacle to conventional chemotherapeutic drugs, since many brain tumors have a disrupted function. Heterogeneity of tumors, cellular kinetics, methods of administration and ways of eliminating drugs play a more significant role than the blood-brain barrier in determining the sensitivity of a specific tumor to chemotherapy drugs. Less sensitive to chemotherapy tumors with a low mitotic index and slow growth, more rapidly growing tumors with a high mitotic index are more sensitive.
Since 1979, within the framework of SIOP, experimental and clinical development of methods of complex treatment of brain tumors in children with the use of chemotherapy have been started. It has been shown that in this situation more than 20 modern cytostatics are effective, including nitrosoureas (CCNU, BCNU, ACNU), methotrexate, cyclophosphamide, ifosfamide, etoposide, teniposide, thiotepa, temozolomide, and alkaloids of pink vinus (vincristine, vinblastine) and platinum preparations. The introduction of chemotherapy directly into the cerebrospinal fluid allows obtaining a much higher concentration of drugs both in the cerebrospinal fluid and in the surrounding brain tissues. This method of administration is most applicable in young children with a high risk of metastasis along the liquor ways and the impossibility of radiotherapy.
Traditionally, chemotherapy is used as adjuvant after operative-beam treatment.
Until recently, the use of chemotherapy for relapse was limited (only some drugs were used). Currently, almost all authors point to the high direct efficacy of a combination of chemotherapy in relapse medulloblastoma (the effectiveness of treatment in the first 3 months is 80%).