Metastatic Bone Disease: When Cancer Spreads to the Bones

Being told that cancer has spread to the bones can feel overwhelming. Along with concerns about the cancer itself, patients may worry about pain, movement and whether the affected bone could break.

Metastatic bone disease can weaken the skeleton, but treatments are available to relieve pain, protect vulnerable bones and help patients remain mobile. Early assessment is particularly important when a bone is at risk of fracture, as protecting it before it breaks allows treatment to be planned and carried out in a more controlled setting.

When a bone fractures because of cancer, the resulting pain, emergency transport to hospital and potentially out-of-hours treatment can make an already difficult experience significantly more distressing for the patient.

Dr Thomas Hilton, an orthopaedic oncologist in Cape Town, explains what metastatic bone disease means, the symptoms to look out for and how treatment is planned.

What is metastatic bone disease?

Metastatic bone disease occurs when cancer cells spread from another part of the body or primary cancer site to one or more bones in the skeleton. This is also called bone metastasis or secondary cancer in the bone.

It is different from a primary bone cancer, which begins in the bone itself.

For example, breast cancer that spreads to the thigh bone is still breast cancer. The cells within the bone metastasis are breast cancer cells, and treatment is planned according to the cancer in which they originated.

Cancer can spread through the bloodstream or lymphatic system. Although many cancers can spread to the skeleton, bone metastases are more commonly associated with cancers of the:

• Breast

• Prostate

• Lung

• Kidney

• Thyroid

Multiple myeloma can also affect and weaken bones, although it is a cancer of plasma cells rather than a bone metastasis and originates in the bone.

Where in the skeleton does metastatic bone disease occur?

Cancer can spread to almost any bone, but metastatic bone disease is often found in the:

• Spine

• Pelvis

• Ribs

• Upper part of the femur or thigh bone

• Upper arm

• Skull

The location matters because some bones carry more weight or play a greater role in movement. A metastasis in the thigh bone, for example, may affect walking and place the bone at risk of breaking as the weakened bone is subjected to the weight of the body. This is different to the humerus or upper arm bone where there is not a lot of weight put through the bone.

A spinal metastasis may cause pain and, in some cases, place pressure on the spinal cord or nerves.

What are the symptoms of metastatic bone disease?

Some bone metastases are discovered on scans before they cause any symptoms. For others, the first sign may be ongoing pain in a particular area that doesn’t seem to improve or go away.

Symptoms may include:

• Pain in a specific area of the bone. It is often a deep aching type of pain.

• Pain that becomes more persistent over time

• Pain that is worse at night

• Pain when standing, walking or using the affected limb

• New back or neck pain

• Weakness or difficulty using an arm or leg

• A fracture following a minor injury or normal activity

• Reduced mobility

Pain does not always mean that a bone is about to break. However, pain that becomes worse when weight is placed through a leg or when an arm is used can indicate that the bone has become mechanically weaker and should be assessed.

New or changing bone pain should be reported to the treating oncology team, particularly in someone with a current or previous cancer diagnosis.

How can metastatic disease weaken a bone?

Bone is living tissue that is continually being broken down and rebuilt. Cancer cells can disrupt this natural process. They also take up space in the bone and replace it with cancer cells that are not strong like bone.

Some bone metastases cause excessive bone breakdown, creating weakened areas within the skeleton. Others stimulate abnormal bone formation. Some produce a combination of both changes.

Even when new bone appears to be forming, it may not have the same strength or structure as healthy bone. The affected area can therefore become vulnerable to collapse or fracture.

What is a pathological fracture?

A pathological fracture is a broken bone that occurs because an underlying condition, such as metastatic bone disease, has weakened it.

Unlike a typical fracture caused by a significant fall or accident, a pathological fracture may occur during an everyday activity. Standing, turning in bed, lifting an object that doesn’t have to be heavy or placing weight through the affected limb may be enough to break a severely weakened bone.

A pathological fracture can cause sudden pain, loss of mobility and a need for urgent surgery. It may also interrupt or delay other cancer treatment.

Where possible, the goal is to identify and stabilise a vulnerable bone before it breaks. This is known as prophylactic fixation.

Signs that a bone may be at risk of fracture

A bone affected by metastatic disease may need urgent assessment if:

• Pain is becoming progressively worse

• Pain increases when standing, walking or using the limb

• The patient begins limping or avoiding weight on the limb

• There is sudden difficulty using an arm or leg

• Imaging shows significant destruction of a weight-bearing bone

• Pain is no longer adequately controlled

• Feeling pain even when resting

• A crack or partial fracture is visible on imaging

Not every bone metastasis requires surgery. The risk depends on the location and size of the lesion, the amount of bone affected, the type of cancer and the patient’s overall health and treatment plan.

When bone pain may be an emergency

Metastatic disease in the spine can sometimes place pressure on the spinal cord. This is known as metastatic spinal cord compression and requires urgent medical attention.

Seek immediate medical care if new back or neck pain is accompanied by:

• Weakness in the arms or legs

• Numbness or tingling

• Difficulty walking

• Loss of balance

• Changes in bladder or bowel control

• Difficulty passing urine

Sudden severe pain in an arm or leg, particularly with an inability to stand, walk or use the limb, may also indicate a fracture and should be assessed urgently.

How is metastatic bone disease diagnosed?

Investigation usually begins with a review of the patient’s symptoms, cancer history and previous scans. The affected area is then examined for tenderness, swelling, weakness and pain during movement or weight-bearing.

Further investigations may include:

How is metastatic bone disease treated?

Treatment is personalised according to:

• Where the original cancer began

• Which bones are affected

• Whether the disease is limited to one area or more widespread

• The degree of pain

• The risk of fracture

• The patient’s mobility and general health

• Other cancer treatments being received

Care is usually coordinated by a multidisciplinary team. This may include medical and radiation oncologists, an orthopaedic oncologist, radiologists, pathologists, physiotherapists and a pain or palliative care team.

Treating the underlying cancer

Systemic treatments work throughout the body and are selected according to the original cancer. These may include:

• Chemotherapy

• Hormone therapy

• Targeted therapy

• Immunotherapy

By controlling the underlying cancer, these treatments may also slow or reduce its effect on the bones.

Radiotherapy

Radiotherapy is commonly used to treat painful bone metastases. It can relieve pain and help control tumour growth in the treated area.

Radiotherapy may be used on its own or following surgery. Although it can help prevent further tumour-related damage, it does not immediately restore the mechanical strength of a severely weakened bone.

If a weight-bearing bone is at significant risk of fracture, surgical stabilisation may be needed before radiotherapy.

Bone-strengthening medication

Medicines such as bisphosphonates or denosumab may be used for certain cancers. These treatments can reduce bone breakdown and lower the risk of complications such as fractures.

They are not suitable for every patient. Kidney function, calcium levels and dental health may need to be assessed before treatment begins.

When is surgery needed?

Surgery may be considered when:

• A bone has already fractured

• A weight-bearing bone is at high risk of fracture

• Pain is caused by mechanical weakness

• The affected bone can no longer safely support normal movement

• A tumour is placing pressure on the spinal cord or nerves

• Stabilisation could help preserve mobility and independence

The purpose of surgery is often to stabilise the bone, relieve pain and allow the patient to move more safely - with the goal of getting the patient back home and functioning as well as possible so that they can enjoy life.

Depending on the location and extent of the disease, surgery may involve:

• Plates, screws or rods to strengthen the bone

• A nail placed inside the bone

• Bone cement to reinforce a weakened area

• Replacement of part of a joint or bone

• Surgery to stabilise the spine or relieve pressure on nerves

The reconstruction must be strong enough to provide lasting support, as bone affected by metastatic disease may not heal in the same way as a straightforward traumatic fracture.

Why treating the bone before it breaks matters

When a weakened bone is identified early, it may be possible to stabilise it through a planned procedure before a fracture occurs.

Preventative surgery is generally more controlled than emergency surgery after a break. It may involve a shorter operation, less blood loss and an easier recovery. Most importantly, it can help the patient maintain mobility and continue other cancer treatments with fewer interruptions.

This is why new pain in a weight-bearing bone should not be dismissed or managed with pain medication alone without understanding its cause.

Maintaining movement and quality of life

Treatment for metastatic bone disease is not only focused on what appears on a scan. It also considers what matters to the individual patient.

The goals may include:

• Relieving pain

• Preventing a fracture

• Preserving the ability to walk

• Maintaining independence

• Making everyday movement safer

• Supporting ongoing cancer treatment

• Improving quality of life

Physiotherapy, mobility aids and practical changes at home may form part of the treatment plan. Patients should follow their medical team’s advice about how much weight can safely be placed through the affected limb.

Living with metastatic bone disease

A diagnosis of metastatic bone disease can bring uncertainty, but patients should not feel that pain or loss of movement must simply be accepted.

There are several ways to control symptoms, protect the skeleton and support mobility. Treatment decisions are made according to the individual patient, the behaviour of the cancer and the role the affected bone plays in daily life.

If you have cancer and develop new or worsening bone pain, particularly pain when standing, walking or using a limb, speak to your treating team. Early assessment can help identify a vulnerable bone before it fractures.

Dr Thomas Hilton provides specialist assessment and surgical management of metastatic bone disease and other complex bone tumours in Cape Town. Working alongside the patient’s oncology team, the aim is to protect movement, reduce pain and plan treatment carefully from the beginning.

Contact Dr Hilton’s rooms to arrange an assessment in Cape Town.

This article provides general educational information and does not replace an examination, diagnosis or personalised medical advice. Sudden weakness, loss of bladder or bowel control, or suspected fracture requires urgent medical assessment.