In some forms of cancer the disease can spread from the original site of the tumour. The place in which the cancer first starts is known as the primary site and this tumour is referred to as the primary tumour. Cells are able to break away from the primary tumour and spread distantly from the original cancer site, through the blood circulation, lymphatic system or spinal fluid. This can involve either a single lesion (Metastasis) or multiple tumours (Metastases). Metastases can in theory spread to any point in the body, but for the purposes of Gamma Knife, only brain metastases are suitable for treatment. These are then deposited in another area of the body where they grow and form another tumour. These tumours are referred to as metastases or secondary tumours. These metastases may be described as being solitary i.e. one only, or multiple where there are two or more. The most common types of cancers that can spread to the brain originate in the lung, breast, colon, skin (melanoma) and kidney.
Treatment is directed towards not only metastatic brain tumours but their symptoms as well. Longer survival, improved quality of life and stabilisation of neurocognitive function for patients with brain metastasis is the goal of treatment. There have been numerous advances in the treatment of metastatic brain tumours and radiosurgery has become an important treatment option. Not all patients are suitable for Radiosurgery, as the size, number and location of the lesions play a deciding role in the most suitable treatment method. An important factor is also that any disease present in the rest of the body should be controlled. Suitability is determined by a multi-disciplinary team comprising consultant neurosurgeons, oncologists and neuro-radiologists; medical physicists and radiographers.
Symptoms can include:
Nausea and vomiting
Weakness or numbness in parts of the body, such as the face, arms or legs
Problems with memory and confusion
Changes in behaviour and personality
Problems with balance and coordination
Loss of bladder or bowel control (called incontinence)
Problems with speech
Problems with swallowing
The symptoms experienced will depend upon which area of the brain is affected by the secondary tumour. Patients may have many different emotions including anxiety and fear. These are all normal reactions and are part of the process that many people go through in trying to come to terms with their condition.
What are the causes?
Metastatic brain tumours begin when cancer located in another organ of the body spreads to the brain. If your cancer started in your lung and has spread to your brain, the areas of cancer in the brain are made up of lung cancer cells.
This is different from having a cancer that first started in the brain (a primary brain cancer). In that case, the cancer is made up of brain cells that have become cancerous. Some people with brain metastases have no signs or symptoms and they are discovered during investigations of their primary tumour. Sometimes brain metastases are found before the primary cancer has been diagnosed. In a small number of cases it may not be possible to find the original cancer. In this situation, the tumour is known as a secondary brain tumour from an unknown primary.
How common are metastatic brain tumours?
As more effective cancer diagnostics and treatments are developed, and as larger numbers of cancer patients live longer, an increasing number of patients are diagnosed with metastatic brain tumours. Estimates of incidence vary and could be some 630 cases per million population with 40% suitable for treatment with radiosurgery. They are the most common brain tumour in adults. Sex differences play a role with lung, colon and renal cancers accounting for 80% of metastatic brain tumours in men, and breast, lung, colon and melanoma cancers accounting for 80% of metastatic brain tumours in women.
You may have a number of tests to diagnose secondary brain cancer. Your doctor will examine you thoroughly. They will test your reflexes and may test the power and feeling in your arms and legs. They may also look into your eyes using a special light and lens (ophthalmoscope), to see if the nerve at the back of the eye is swollen. This can be a sign of raised pressure on the brain caused by a tumour.
You will have a brain CT or MRI scan. Sometimes you will have a biopsy, if a tumour is found by the scans.
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