Brain is one of the most common distant metastatic sites of lung cancer, and the incidence of brain metastasis has gradually increased in recent years, which may be related to the wide application of imaging diagnostic techniques in clinical practice and the prolonged survival of tumor patients. Brain metastasis is one of the most common sites of metastasis in lung cancer patients. 7.4%-10% of non-small cell lung cancer patients have brain metastasis at the first consultation, and about 30%-50% of patients will have brain metastasis during the treatment process. The clinical manifestations and diagnostic methods in this small article can be generalized in both non-small cell lung cancer and small cell lung cancer, while the treatment is mainly for non-small cell lung cancer.
What will be the clinical manifestations of brain metastasis?
1. Headache: Headache in brain metastasis is mainly caused by increased intracranial pressure or cerebral edema, and has the following characteristics: ① aggravated in the early morning or at rest; ② accompanied by nausea and vomiting; ③ aggravated by cough or tension; ④ accompanied by impaired consciousness or drowsiness.
2. Vomiting: Due to the increase of intracranial pressure, the medulla oblongata respiratory center is stimulated, resulting in vomiting, which mostly occurs when the headache is intense and is jet-like.
3.Visual impairment: The increased intracranial pressure will cause poor venous blood flow back to the eye, resulting in bruising and edema, which will damage the visual cells on the retina in the fundus of the eye and cause vision loss.
4. Mental abnormalities: Brain tumors located in the frontal lobe of the brain can disrupt the mental activities of the frontal lobe, causing mental abnormalities such as excitement, agitation, depression, repression, forgetfulness and fiction.
5.Unilateral limb sensory abnormalities or weakness: The parietal lobe located in the middle of the cerebral hemisphere is specialized in sensory management, and tumors in this part often cause unilateral limb pain, temperature, vibration and form discrimination sensation to be reduced or disappeared.
6.Phantom smell: Tumor in the temporal lobe can cause phantom smell under its stimulation, which can smell an odor that does not exist, such as burnt rice or burnt rubber.
7. Hemiplegia or staggering gait: Cerebellar lesions are more specific, i.e. patients often develop hemiplegia or staggering drunken gait after headache, vomiting and visual impairment.
8. Tinnitus and deafness: This kind of manifestation is mostly found when talking on the phone, i.e., one ear can hear but the other ear can’t. This manifestation is mostly the precursor of auditory neuroma.
There are various manifestations of brain metastasis of lung cancer. When the above symptoms appear, patients should go to hospital for detailed examination.
How to diagnose brain metastasis?
1. Enhanced MRI is the gold standard for intracranial tumor diagnosis. It can provide the clearest image of tumor and is more sensitive than CT (including enhanced CT) for microscopic lesions, edema and meningioma, especially those located in brain stem and posterior cranial fossa; it has advantages in differentiating brain metastasis from brain abscess and traumatic brain injury; it can grade tumor or evaluate treatment effect.
2.PET-CT can evaluate the metabolism of tumor and normal tissue, distinguish between radiation necrosis or tumor recurrence; show the best target area for biopsy and grade tumor at the same time.
3.If enhanced MRI shows soft meningeal enhancement, lumbar puncture is highly recommended. Contraindications for lumbar puncture: increased brain pressure due to obstructive brain edema, displacement of midline structures or any indication of posterior cranial fossa occupancy.
4. Cerebrospinal fluid examination with malignant tumor cells visible on cytological examination.
What are the treatment means of brain metastasis?
1.Surgery and radiotherapy are the cornerstones of brain metastasis treatment
When patients have 1-3 brain metastases, surgery±wholebrainradiotherapy (WBRT) or stereotactic radiotherapy±WBRT is the treatment option.
In patients with multiple brain metastases (≥4), whole-brain radiotherapy is the current standard of care, with a recommended dose of 30 Gy/10f. Whole-brain radiotherapy can improve neurological symptoms in 70% of patients, with a near-term efficiency of 80% and a one-year survival of 10%-20%.
2.Chemotherapy
Temozolomide, a new alkylating agent, is a small-molecule, lipid-soluble oral chemotherapy drug with good central/cerebrospinal fluid permeability, 100% bioavailability and high blood-brain barrier permeability (about 30%-40% of plasma concentration), which can be spontaneously converted into active metabolites after entering the center, with low side effects and radiotherapy sensitizing effect. Temozolomide can be used alone, in combination with other chemotherapeutic agents and in combination with radiotherapy or sequential surgery or radiotherapy.
Pemetrexed, an anti-folate agent with a core of pyrrolopyrimidine moieties in its structure, has been shown to be effective in both intracranial and extracranial lesions of asymptomatic brain metastases.
Nitrosoureas (carmustine, formustine, lomustine) and teniposide do have high concentrations in brain metastases and are effective in brain metastases.
Topotecan, an inhibitor of topoisomerase-I, is a semi-synthetic camptothecin. Current research shows that it can enter the blood-brain barrier and has good effect on lung cancer brain metastases
3.Targeted therapy
Epidermal growth factor receptor tyrosine kinase inhibitor, mesenchymal lymphoma kinase, inhibitor bevacizumab and some immune-targeted drugs are effective for brain metastases.