When does brain stem glioma need radiotherapy?

When does brain stem glioma need radiotherapy?

When does brain stem glioma need radiotherapy? Do brainstem gliomas need radiotherapy?

The specific classification of brainstem glioma is generally difficult to operate for brainstem glioma, and its treatment is based on comprehensive treatment, including new therapies such as surgery, radiotherapy, chemotherapy, gene targeted therapy, and immunotherapy. Generally speaking, radiotherapy is the standard treatment for DIPGs, but it can only temporarily improve symptoms and cannot prolong their overall survival.

Chemotherapy is effective for partial recurrence or residual PAs after surgery, but various chemotherapy regimens have not significantly improved the prognosis of DIPGs. Surgery can significantly improve the prognosis of exogenous and focal low-grade tumors.

1. Indications for radiotherapy:

• DIPGs;
• High-level BSG;
• Low-level BSG:

(1) Exogenous type (type Ⅰ) and focal endogenous type (type Ⅱa): After total tumor resection, it should be closely observed, and radiotherapy is possible for tumor progression; partial resection or biopsy, depending on the molecular pathology results, choose radiotherapy and Or) Chemotherapy, or regular observation, and treatment when the tumor progresses.

(2) Canopy type (Type Ⅲa), aqueduct type (Type Ⅲb) and NF-1 related (Type Ⅲc) BSG: It can be preferably observed. When the tumor progresses, choose surgical resection or stereotactic biopsy to clarify histopathology and molecular Pathological type, guide follow-up treatment.

2. Relative contraindications of radiotherapy:

• Those who are less than 3 years old;
• Persons with poor general condition or severe brainstem failure and unable to tolerate radiotherapy;
• Those who have severe hydrocephalus that have not been treated;
• The wound has not healed or the infection is locally present;
• It is recommended to choose radiotherapy after the pathological diagnosis is as clear as possible to avoid misdiagnosis and treatment.

3. Radiotherapy program: Radiotherapy cannot prolong the overall survival of most patients, but can only relieve symptoms in a short time. The remission period of symptoms varies with the pathological level.

(1) Formulation of the target area:

t is strongly recommended that qualified units use CT and/or MRI simulation positioning, and CT/MR/PET-CT image fusion in order to accurately delineate the target area. When determining the target area, refer to the preoperative , Postoperative and recent MRI data and PET-CT results.

(2) Treatment plan:

The prescribed dose is defined by 95% of the target volume. Depending on the size of the irradiation volume, a dose of 54-60 Gy is recommended and divided into 1.8-2 Gy each time. Most studies have shown that the total dose of conventional radiotherapy> 60 Gy has no clinical benefit. Three-dimensional conformal radiotherapy or intensity-modulated radiotherapy is recommended. Precise radiotherapy can better protect normal brain tissue and reduce radiation damage.

• ①High-grade BSG: Radiotherapy should be started as soon as possible after the diagnosis is clear. The conventional divided dose is 1.8-2.0 Gy/time, 5 times/week, and the standard dose is 54-60 Gy/30-33 times. It is recommended to irradiate the tumor locally. The clinical target volume (CTV) is the gross target volume (GTV) that is the abnormal area on FLAIR/T2WI, plus 1.5 to 2.0 cm. The boundary of 0.3～0.5 cm outside the CTV is the planning organ risk volume (PTV);
• ②Low-grade BSG: Determine the tumor volume based on preoperative and postoperative MRI. The FLAIR image or abnormal signal on T2WI is usually used as GTV. CTV is GTV with 1～2 cm distance. The total dose for low-grade glioma is 45～ 54 Gy/25-30 times, 1.8 Gy/time.

(3) Radiotherapy reaction: Adverse reactions of radiotherapy are divided into 3 different types according to the time of occurrence and clinical manifestations:

• Acute (occurs within 6 weeks after radiotherapy),
• Subacute (occurs 6 weeks to 6 months after radiotherapy)
• Late stage (months to years after radiotherapy).

Acute and subacute radiation injury may be caused by vasodilation, damage to the blood-brain barrier and edema. The acute reaction of brainstem radiotherapy is manifested as aggravation of previous neurological dysfunction or new neurological dysfunction; MRI manifests as thickening of the brainstem and diffuse edema. The application of glucocorticoid can relieve the symptoms.

If there are changes in breathing, heartbeat frequency and rhythm after radiotherapy for medullary tumors, the risk of death from radiotherapy is significantly increased. Brainstem edema that is difficult to control during or after radiotherapy can be treated with targeted anti-angiogenic drugs to relieve symptoms.

Pseudoprogression usually occurs within 2 to 3 months after temozolomide concurrent radiotherapy and chemotherapy. It is a subacute radiation reaction. The pathological changes are early radiation necrosis, and most of them can be cured by themselves. Late radiation reactions are often progressive and irreversible radiation necrosis, which is manifested as the continuous deterioration of neurological dysfunction and should be avoided as much as possible.

Stereotactic radiosurgery (SRS)

SRS is a special form of radiotherapy. Under the guidance of a stereotactic headgear, a one-time high-dose radiation or a large split dose (≤5 times) is precisely focused on the target area, which can effectively kill tumor cells, and its mechanical error In the millimeter range, very common equipment includes gamma knife, cyber knife, modified linear accelerator and proton beam equipment.

This kind of single or high fractional dose SRS treatment generally requires a small tumor volume and clear boundaries. From the perspective of evidence-based medicine, currently only grade IV and grade V evidence-based medicine support the gamma knife treatment of certain BSG.

• 1. Indications: SRS is suitable for the treatment of residual or recurring localized gliomas after surgery and/or radiotherapy, especially low-grade gliomas with relatively clear boundaries such as PAs.
• 2. Contraindications: DIPGs should not be treated with stereotactic radiotherapy.

3. Treatment plan:

(1) Positioning:

MRI-enhanced thin-scan spoiler gradient echo sequence and T2 sequence are very common positioning sequences. Currently, multi-modal image fusion positioning such as CT, MRI and PET can be realized.

(2) Dosimetry:

Usually a 50% isodose curve is used to cover the periphery of the lesion, and the central and peripheral doses are formulated according to the nature of the lesion, the size of the lesion, and the structure around the lesion. The dose to the normal brain stem of a single irradiation treatment does not exceed 15 Gy. The peripheral prescription dose depends on the size of the lesion, and the dose range is 12-16 Gy. If the patient has received other radiotherapy before surgery, the therapeutic dose should be adjusted according to the radiotherapy history.

(3) Postoperative treatment:

It is recommended to give intravenous methylprednisolone 40 mg or dexamethasone 10 mg before or after treatment. Local disinfection and anti-inflammatory treatment should be performed on the pierced area of ​​the head nail, and antibiotics should be given if necessary.

4. Adverse reactions:

• (1) Radiation brain edema: mannitol, glucocorticoid, bevacizumab, hyperbaric oxygen, etc. can be used to reduce brain edema.
• (2) Obstructive hydrocephalus: It is recommended to perform ventricular-abdominal shunt surgery in time.
• (3) Neurological impairment or focal neurological impairment: general neurotrophic and supportive treatment, including drug therapy and hyperbaric oxygen.

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