Brain Cancer
了解腦癌成因、症狀，有效預防和診療，提高存活率
腦癌 (Brain cancer) 在香港並不常見，起源於腦部的惡性腫瘤，成因很可能和年齡、性別、遺傳、長期接觸或曝露於化學物質有關。腦癌症狀比較難以察覺，但只要腦腫瘤生長到一定體積，腦部功能就會受到不同程度的影響，診療腦腫瘤亦比其他癌症困難。及早檢查發現及診療，對存活率至為重要。因腦瘤生長極具擴散侵犯性，雖然可以做切除處理大部分的腫瘤，但切除後的化學診療，卻會被腦部特有的「血腦障壁」阻隔，而無法產生療效，造成腦癌不斷復發，從而影響存活率。
根據香港癌症資料統計中心發佈的最新數據，在1,122宗腦腫瘤新症中，約有23.6%為惡性腫瘤（即約265宗為腦癌）。以一至四級惡性程度來說，第一級兩年後的存活率有九成，第二級有六成，第三級有五成，第四級根治機會很微，即使用盡各種診療，大部分都會復發，兩年存活率少於三成，五年存活率則更差，約只有半成。
Symptoms of Brain Cancer
The brain controls different parts of the body, so the symptoms are closely related to the location of the tumor. Some patients may have no symptoms at all and unexpectedly discover the tumor in their regular physical examination, while others may have more than one of the following four major brain cancer symptoms at the same time.
- Increased intracranial pressure: Patients with this symptom may suffer from headaches, vomiting, visual disturbances and impaired consciousness.
- Frequent headaches: the sensation of dull pain, which is aggravated by coughing, sneezing and going to the toilet. In the early stage, the headache usually occurs only when patients wake up in the morning; in the advanced stage, the headache becomes more persistent and severe.
- Projectile vomiting: Brain cancer can cause sudden and severe vomiting, which is not always preceded by headache and nausea.
- Visual disturbances: Patients may experience blurred vision, double vision, or even vision loss.
- Impaired consciousness: Reduced cerebral blood flow and damaged brainstem function can lead to impaired consciousness. If the tumour is growing rapidly, it can cause cerebral oedema and make the patient fall into a coma in a short period of time.
- Epilepsy: Symptoms of almost any type of epilepsy can be seen in patients with brain tumours, including localised or generalised seizures.
- Endocrine disorders: Endocrine disorders cause abnormalities in growth, body shape and sexual function. For example, the tumour may compress parts of the brain and reduce hormone production.
- Focal neurological deficits: such as weakness or inflexibility of one limb, abnormal sensation in one side of the body, loss of balance, speech difficulty, changes in temperament, and visual field deficits.
Causes of Brain Cancer
The medical field is still uncertain about the cause of brain cancer, but may associate it with the following factors
- Age: People of all ages are at risk of developing brain cancer, while people above 40 years old have a higher risk.
- Gender: Men are more likely to develop the cancer
- Hereditary factor: A family medical history of glioma
- Long-term exposure to chemical substances: People who are persistently exposed to radioactive substances and those who work with chemicals have a higher risk of developing the cancer.
Survival Rate for Brain Cancer
Screening of Brain Cancer
If the doctor suspects the occurrence of brain cancer, a series of examinations will be conducted to diagnose whether the patient has brain cancer. These tests include clinical examination and tumor diagnosis, computed tomography scan (CT scan), magnetic resonance imaging (MRI), positron emission tomography (PET), angiography, photoacoustic imaging, brain biopsy, etc.
- Clinical examination: The doctor needs to obtain a detailed medical history to understand the patient's symptoms and the impacts on their daily life. The nervous system of the patient will be examined particularly to track the development of the disease.
- The knee-jerk and other reflexes
- Muscle strength and tone of the hands and feet, and their response to needle pinching
- Brain tests by answering simple maths questions
- Vision examination by observing the optic nerve endings with a device to determine if the intracranial pressure is high
- Examine the eyes with an eye examiner for any swelling of the optic disc at the back of the eye, and carry out a comprehensive vision test.
- Hearing test
- Facial muscle test, including smiling
- Test the tongue movement and response by using a mouth gag to press down the tongue
Diagnosis of Brain Cancer
After the initial examination, the doctor will use imaging tests and pathological analysis to diagnose whether the patient has brain cancer and identify the stage of cancer, if any:
Imaging tests:
- Computed tomography scan (CT scan)
CT Scan is a radiological imaging modality that involves the intravenous injection of an iodinated contrast agent to show the approximate location of the tumor and its effects.
- Magnetic resonance imaging (MRI)
不含放射性物質，能清楚顯示腫瘤的詳細情況，準確度達90%，並有助日後診療時定位，及導航放射診療。磁力共振掃描特別有助於診斷星形膠質瘤，而對於顱後窩腫瘤尤其是腦幹腫瘤，亦以磁力共振掃描較準確。
- Positron emission tomography (PET)
It can show the metabolic activity of the cells and help to assess the type, grade, and degree of metastasis of the tumor. It is generally recommended for patients with metastatic tumors to track the location of the primary tumor.
Pathological Analysis:
最準確和可靠的方法。通常在切割期間取出腫瘤組織樣本進行病理化驗以確定類型和嚴重性級別，又稱為「組織活檢。然而，有時候當腫瘤的位置深潛或者當切割的風險太高，則會考慮用立體定位穿刺術來獲取組織樣本作病理分析，此做法對病人較為安全，但穿刺拿取的樣本亦相對會較小。
腦癌診療
腦癌的診療方法主要是結合腦外科切割，再配合療程後電療及化療，以減低復發風險，有時候亦會採用標靶診療和最新的電場診療。醫生會根據患者的情況來擬定診療方式。
- 切除療程
切除療程是診療腦癌的法，最理想的效果是將整個腫瘤連同周邊癌細胞組織一同割除，但要將腫瘤完全切除是十分困難的，因為以不損害腦部功能和造成嚴重併發症的大前提下，很多時只能在安全範圍內盡量移除腫瘤，以減低顱內的壓力及減輕患者痛苦。有時候，醫生在評估患者的病情後，可能只能切除大部分的腫瘤，而剩餘的部分就需要利用放射診療和化學診療來進一步清除。
- 放射診療
採用先進放射技術集中高能量放射線破壞癌細胞，阻止生長和擴散。近年，較先進的放射診療技術如強度調控放射診療、影像導航放射診療等技術能提升放射劑量，有效殺死腫瘤的同時，又能減低對周邊正常組織的破壞。
- 化學診療
以抗癌藥物來破壞癌細胞，常用的口服Chemo藥為「替莫唑胺」(temozolomide, TMZ), 能夠穿透血路屏障攻擊癌細胞。研究指出，患者在術後接受放射診療合併TMZ，能有效延長其存活率。
- 腫瘤電場診療(TTF)
TTF是嶄新的腦癌診療技術，患者需要每天至少18小時在頭皮上貼上4塊電極貼，透過製造出來的電場干擾腦部癌細胞，使它們無法正常分裂，從而阻止癌細胞生長，可以與化療藥物同步使用。
- 標靶診療
常用於診療腦癌的標靶藥物為「貝伐珠單抗」（Bevacizumab），是一種對抗血管內皮細胞生長因子（簡稱VEGF）的單株抗體，作用是透過抑制腫瘤的血管新生，從而截斷腫瘤所需的養分供應，達到抑制腫瘤生長的目的。
Recovery and Rehabilitation of Brain cancer
- Rehabilitation
- Maintain a balanced diet, eat less irritating food, and quit smoking and drinking.
- Maintain a cheerful state of mind and relieve stress
- Regular follow-up consultation
Prevention of Brain Cancer
The major prevention of brain cancer is to avoid high-risk environmental factors. The followings are some recommendations:
- Self-protection for high-risk employees
People who are constantly exposed to pathogenic factors in environments such as chemical or nuclear industries should take self-protection measures such as wearing gloves, masks, and radiation protective equipment.
- Avoid excessive use of mobile devices
Although no conclusive evidence can prove that the heavy use of mobile devices is the culprit of brain cancer, excessive use should be avoided since electromagnetic waves may damage the human body
Brain Cancer FAQ
Q. What is the survival rate for brain cancer?
In the United States, the 5-year survival rate for patients with brain cancer or central nervous system tumor (CNS tumor) is about 36%, and the 10-year survival rate is about 31%. Age is one of the factors that affect the general survival rate after the diagnosis of brain cancer or CNS tumor. The 5-year survival rate for people under 15 years old is about 75%.
Q. Can brain cancer be cured?
It depends on the location, size and grade of the malignant brain tumor. It is possible to cure if the tumor is detected early. However, brain tumor often recurs and sometimes cannot be removed.
Q. What will happen when you suffer from brain cancer?
The brain is responsible for every body function including vision, hearing, speech and movement. As the tumor develops, it may compress and destroy the tissues that control these body functions. This can lead to complications such as headaches, seizures, vision and hearing loss, and equilibrium problems.
