Metastasis

Metastasis

Cancer often leaves us flooded with emotions when we hear about someone affected by such a devastating disease. It occurs due to the uncontrolled division of cells, which can destroy normal tissues and potentially spread to other parts of the body. This process of cancer invading other parts from where it has started is known as metastasis, and when it spreads to bones, it is called bone metastasis.

Bones are frequent sites for metastasis, which once it happens may become challenging to cure. Bone metastasis may appear similar to that of cancer that has started in the bone (primary bone cancer). However, the cells in the metastasized bone tumors are not made of bone cells but are from the original tumor sites from where they have spread. The majority of bone metastases are due to prostrate or breast cancers that can metastasize to any bone, of which the spine remains the most common site. Other sites may include the pelvis, upper leg bone (femur), upper arm bone (humerus), ribs, and skull.

What are the types of bone metastasis?

The tumors that metastasize to bones can be categorized depending on how they affect the bones. They may:

• Create holes in the bones, making them fragile, weak, and vulnerable to fractures known as osteolytic lesions.
• Lead to abnormal (calcified or mineralized) depositions of the bone that are weak and unstable known as osteosclerotic or osteoblastic lesions.
• Cause both osteolytic and osteoblastic lesions, known as mixed lesions.

What are the symptoms of bone metastases?

The tumours of the bones may cause the following symptoms:

• Pain
  • Intermittent pain that may be relieved with movement
  • Worsen during night
  • Gradually increase and becomes constant
• Weakness
  • Bones that are more prone to breaking than others
• Nerve compression or damage (spinal cord)
  • Back pain
  • Numbness in the legs
  • Bowel and bladder problems
• Calcium leak from the bones, leading to high calcium levels in the blood (hypercalcemia) that may cause
  • Nausea
  • Loss of appetite
  • Constipation
  • Extreme thirst
  • Frequent urination
  • Dehydration
  • Fatigue
  • Confusion
• Drop in red blood cells (if bone marrow is affected ) leading to
  • Tiredness
  • Weakness
  • Shortness of breath

What are the causes of bone metastasis?

Bones are the third-most common site for metastasis after the lungs and liver. The reason for metastasis is still unknown. The most common cancers that may metastasize include:

• Prostate cancer
• Breast cancer
• Lung cancer
• Lymphoma
• Thyroid cancer
• Kidney cancer
• Multiple myleoma

How is bone metastasis diagnosed?

The following tests may help to identify if the cancer has metastasized to the bones or to identify the cause when you have the symptoms of bone metastasis.

• X-ray: X-rays may help identify if the bones appear less dense (osteolytic), more dense (osteoblastic), both (mixed) or fractures in the bones.
• Bone scan: Minor levels of radioactive material, when injected into the body, are attracted to the diseased bone cells that are shown up more clearly during a bone scan involving your complete skeletal structure.
• Computed tomography (CT): The detailed picture obtained through the cross-sectional images using both X-rays and computer technology helps identify if the cancer has spread to the bones.
• Magnetic resonance imaging (MRI) provides detailed images of bones and other soft tissues. Additionally, it helps to further analyze a bone mass visualized in an X-ray.
• Positron emission tomography (PET): A small dose of radioactive chemical is injected into the blood, which is absorbed by cancerous cells to a greater extent. A PET scanner scans your body and helps identify small tumors, which may be difficult to find with other tests.
• Laboratory examinations: Measurement of substances such as calcium or alkaline phosphatase present in higher amounts than normal during bone metastasis may help in the diagnosis. However, higher levels of these substances do not always relate to bone metastasis.
• Biopsy: A biopsy is a confirmative test performed when imaging or blood tests are abnormal. During the procedure, a bone sample is obtained with the help of a special biopsy needle, which is further examined under a microscope for abnormal cells.

How is bone metastasis treated?

The treatment for bone metastasis may depend on several parameters, such as the extent of spreading, prior treatment, symptoms, and general health. It may follow the same regimen that is used to treat primary cancers, with some additional options. The treatment helps to relieve the symptoms and shrink or slow down the growth of bone metastases, but it cannot cure the condition.

• Medications: Combination of various kinds of medicines such as non-steroidal anti-inflammatory drugs (ibuprofen) or steroids, are prescribed to relieve pain and inflammation.
• Bisphosphonates: Medicines such as bisphosphonates (pamidronate, zoledronic acid) help to slow down abnormal bone formation or destruction and reduce other related symptoms, such as bone pain, high blood calcium levels, and the risk of fractures.
• RANK ligand inhibitors: RANK ligand inhibitors like denosumab injections are administered when bisphosphonates are not able to provide relief. Denosumab is injected under the skin to prevent damage to the bones.
• Hormone therapy: Medications to suppress the hormones are useful in the case of cancers that are sensitive to hormones, such as prostate or breast cancers. They may either act to lower hormone levels or block the interaction between hormones and cancer cells.
• Chemotherapy: When the cancer has spread to multiple bones, chemotherapy is recommended. It involves the use of drugs (oral or intravenous) that fight against cancerous cells throughout the body.
• Intravenous radiation: It involves injecting low levels of radioactive substances (radiopharmaceuticals) into a vein, which are attracted to your bones and travel to the areas of bone metastasis and release radiation.
• Radiation therapy: Strong ionizing X-rays are used to destroy cancerous cells, which further helps to relieve pain and destroy tumor cells. It may also help to prevent fractures and treat spinal cord compression.
• Surgery: Surgery may be recommended to prevent or treat bone fractures. It may involve stabilizing the bones with the help of metal plates, rods, or screws or repairing a fractured bone. Bones that cannot be handled with metal plates can be helped by using bone cement that is injected into the damaged or broken bone.
• Tumour ablation: It involves using a probe that is inserted through your skin and guided to the tumor site. Chemicals, electricity, heat, or cold that are passed through the probe help destroy the tumor.
• Physical therapy: A physical therapist may suggest an exercise regimen that strengthens the bones and improves mobility. He may also recommend assistive devices, such as a walker or brace, to avoid any pressure on the affected bones.

What is the outlook for bone metastasis?

The outlook for bone metastasis depends on the extent and location of the condition. However, it is still possible to maintain a good quality of life through some changes in your daily activities that help reduce pain and the risk of fractures.