Cancer starts in one part of the body such as the breast, lung, etc, and can spread to other areas such as the liver, brain or bones, etc. The place of origin is called the primary site and the areas it has spread to are called secondary sites and cancer there is known as secondary cancer or metastatic cancer.
Bone metastases are areas of secondary cancers in the bone. This is when cancer has spread into the bones from other parts of the body. The cancers that commonly spread to the bones are breast, lung, prostate, kidney, myeloma, and thyroid cancers. Most cancers can spread to the bones, some more common than others.
Bone metastases can be of three types.
Lytic metastases are those where the cancer causes destruction of the bone leading to a less dense picture when seen on the x-ray.
Blastic metastases are those where there is a deposit of cancer in the bone and when seen on the x-ray appears denser than the rest of the normal bone.
Mixed metastases is where the cancer causes both lytic and blastic metastases.
When cancer spreads into the bones, the patient may or may not experience symptoms. But as it increases in the bones, most patients eventually experience symptoms.
This is the most common symptom present in patients having bone metastases. The pain is present when the patient is mobilising or resting. If the metastases are present in the bones of the lower limbs, the pain may be present on walking or weight bearing. If present in the spine, symptoms are present on bending, turning etc. When in the chest or ribs, the pain can get worse with breathing or bending.
The type of pain can also vary depending on the location of the bone metastases. Pain can be dull aching in nature, sharp, or as a burning or pulling type when a nerve is trapped due to the bone metastases.
As a cancer in the bone weakens it, there is a risk of a fracture in the bone particularly those in the limbs. The fracture may happen with minimal or no trauma at all.
Nerve compression or spinal cord compression
When metastases are present in the spine, there is a risk of collapse or a fracture of the vertebrae in the spine. As the spinal cord and other nerves are present in the spine, any change in architecture of the spine can cause damage to these nerves and cause symptoms. Please check the section on spinal cord compression for more information.
Raised Calcium levels
Patients who have metastases in the bones can have an increased calcium level in the blood. This in turn leads to symptoms of weakness, tiredness, confusion, thirst and kidney malfunction.
When bone metastases are suspected, the following tests can be done. Which scan to choose will depend on the condition of the patient. An x-ray, bone scan or MRI is best to look for bone metastases.
Blood tests including CBP, kidney function, liver function tests, calcium and bone profile are commonly done.
X rays of the suspected bones are done to look for presence of metastases and to estimate the risk of a fracture in patients that have pain.
A CT scan is a scan that uses x-rays to give a three-dimensional image of the part of the body that is scanned. It is more accurate than an x-ray in identifying and staging cancer. A contrast enhanced scan is one where an injection is given into the vein prior to the scan and this gives better images. Oral contrast is given to the patient to drink when the abdomen is being scanned. CT scan takes only a few minutes to do. CT scan is also used to help guide the doctor when certain biopsies are done.
An MRI scan uses magnetic fields to generate images and is used very often to diagnose and stage cancer. This scan is done for some types of cancer. MRI produces better images than CT in areas such as brain, spine and pelvis (lower part of abdomen). Some patients find it difficult to have an MRI scan as they can feel claustrophobic while the scan is being done. The time taken for MRI scans is longer ranging from 20 mins to up to an hour. Contrast agent is injected during the scan to get better images. The scan is done as sequences and usually many sequences are done in one scan in cancer patients.
F18 Bone scan
This scan is similar to a PET-CT scan, but the purpose of the scan is to detect presence of cancer in the bones. Bone scans are done after the diagnosis is made and is helpful in staging the cancer. An F18 bone scan is said to be more sensitive than a technetium bone scan in detecting cancer in the bones
Technetium99 Bone scan
This type of scan is also used to look for cancer in the bones and is usually cheaper than an F18 scan.
Pain control is achieved with good pain killers which include drugs such as Paracetamol, NSAID drugs such as Ibuprofen and Diclofenac and in more severe pain, opioid drugs such as Tramadol, Buprenorphine, Morphine, Fentanyl or other opioid drugs. Which drugs to use depend on the severity of the pain and this will be assessed by the doctor.
A course of radiotherapy to the affected bone provides good pain control. Generally, there is a 70%-80% chance of pain control with this procedure. The course of radiotherapy usually last from 1-10 treatments in total. For patients with limited bone metastases in the spine, newer techniques of radiotherapy such as stereotactic body radiotherapy (SBRT) can be very effective.
In patients where there has been a fracture in the bone or there is a high risk of fracture in the near future, surgery to help fix the fracture is a option of treatment. This procedure helps with pain control as well as improves function in the affected limb.
In patients with bone metastases, medications can be given to help strengthen the bones and prevent risk of fractures. A group of drugs called bisphosphonates are commonly used in this setting. They are given into the vein usually. Drugs used are Pamidronate, Zoledronate or Zoledronic acid. These can be given every 3-6 weeks. Some bisphosphonates can be given by mouth but usually the intravenous route is used.
Other group of drugs called osteoclast inhibitors are also used. They tend to be more effective than bisphosphonates but are also more expensive. Drugs from this group such as Denosumab, which is given as an injection is used.
Calcium and Vitamin D in patients with normal or low calcium are used to help strengthen the bones.