What is bone metastasis?
Metastasis is the spread of tumour cells from the organ of origin to other regions of the body. When this spread is to the bones, it is known as bone metastasis. Generally, breast cancer or prostate cancer is more likely to spread to bones. The most common sites for bone metastasis are the spine, femur and pelvic bones. Similar to the lungs, bones are sites for late metastasis. Bone metastasis usually indicates very advanced disease and cannot be cured.
What are its main signs and symptoms?
Sometimes, bone metastasis does not produce any signs or symptoms. When symptoms occur, they are usually related to the bone that is affected.
Nevertheless, there are certain common signs and symptoms of bone metastasis, irrespective of the bone affected. These include:
- Bone pain
- Fracture of the affected bone
- Loss of control over urine and bowel movements
- Weakness or pain in the legs or arms
- Hypercalcaemia (breaking down of the bones leading to increased blood calcium levels) which causes symptoms like
- Nausea
- Constipation
- Mental confusion
- Convulsions
What are its main causes?
When the cancer cells enter the blood or lymph, they go to the distant organs and affect them. These cancer cells can enter the bone and start multiplying inside the bone. During this process, they become parasitic and start taking up nutrients from the bone, making the affected bone fragile.
The commonest cancers that spread to bones are:
- Breast cancer
- Prostate cancer
- Kidney cancer
- Lung cancer
- Lymphoma
- Thyroid cancer
How is it diagnosed and treated?
A thorough medical history and physical examination can hint towards the affected bone. In case of bone metastasis, blood tests are seldom used; imaging techniques help in establishing the final diagnosis. These imaging modalities include:
- X-ray
- Bone scan
- Computed tomography (CT) scan
- Magnetic resonance imaging (MRI) scan
- Positron emission tomography (PET) scan
The goal of treatment is to reduce pain, prevent fractures and avoid further spread to other bones.
Treatment methods used for bone metastasis include:
- Chemotherapy agents – Drugs are used for shrinking the cancer cells
- Hormone therapy – It helps in controlling the primary tumour, like androgen deprivation therapy used for controlling the spread of prostate cancer. It also includes the use of hormones like parathyroid hormone, which help in the repair of fractured bones
- Targeted therapy
- Immunotherapy- It uses immune system cells called immunoglobulins to help kill cancer cells.
- Bisphosphonates – They offer symptomatic relief, as they help in reducing bone pain, reduce blood calcium levels, reduce the risk of fractures and also slow down the damage to the bones
- Radiation therapy – Exposing the affected bones with radioisotopes like strontium-89 and radium-223 can help in killing the cancer cells