The most common symptoms of GCT are:

• Pain
• Swelling around the tumour
• Fractures in the bone caused by bone weakness
• Restricted movement

Depending on your individual situation, your treatment could involve surgery, a biological therapy called Denosumab, or sometimes both.

Surgery

If surgery is performed on your tumour, commonly this is a procedure called curettage. The aim of this is to clean out the GCT from the bone and then to carefully check that no GCT cells are left behind.

The surgeon may then fill the hole left behind when the GCT is removed. This is usually done using a material called bone cement and/or bone graft. Cementing the hole helps to make sure that any remaining GCT cells are killed off through the cement being set by heat and gives immediate support for the bone. Grafting, where bone is taken from another part of the body, is used closer to joint surfaces to try to reduce the risk of arthritis in the future. The affected bone can often be weakened by the GCT, so structural support is often needed to strengthen the bone using a plate and screws.

Sometimes the GCT can destroy a lot of the bone and sometimes the bone is already broken. In this case, your surgeon may advise that the safest option is to remove the entire area of affected bone. This will almost always involve the removal of the end of the long bone and may mean that an artificial joint replacement is needed. This will usually be a specially designed joint replacement like those used for bone cancer patients. Amputation is only used as a treatment option in the most challenging cases.

What are the advantages and disadvantages of these procedures?

The advantage of a curettage, with or without cement or bone graft, is that you get you keep your own joint. The disadvantage is the risk of the tumour coming back. This can be as high as 50%.

The advantage of surgery to remove the affected bone area is that the whole GCT is removed and there is a very low risk of it coming back (less than 5%). The disadvantage is that you will probably need an artificial joint replacement. This will never give you normal function and will be at risk of problems in the future, such as infection, or the artificial joint coming loose and wearing out.

In many situations the surgeon will try curettage as the more conservative option. If that does not work then surgery with reconstruction will be used.

Biological therapy

Biological therapies are treatments that interfere with the way cells work. GCT is sometimes treated with a biological therapy called denosumab.

GCT is caused by giant cells that work like osteoclast cells. These are the cells that break down old bone. GCT cells produce overactive osteoclasts that break down healthy bone cells as well and destroy the bone. Denosumab works by controlling the activity of GCT cells. It can stop bone damage in people who have GCT of the bone and it can be used to shrink a GCT enough so it can be removed safely through surgery.

Most people will start to find that any pain they have reduces within a few weeks of Denosumab treatment. X-rays and scans will show the GCT shrink a bit, then bone will start to reform at the edges of the cavity within a few months.

What are the side effects of Denosumab?

Denosumab was originally used to treat GCTs in places where the tumour could never be surgically removed or where surgery would be disabling, like the spine, skull or pelvis. Denosumab has proved very effective, but there are increasing concerns that it may have long term side effects. These include:

• Osteonecrosis of the jaw – damage to the jaw leading to deep ulcers
• Pain in the long bones when active
• Hypocalcaemia – low calcium levels

Avoiding pregnancy and using contraception for at least five months after stopping treatment is recommended, as is sperm donation prior to treatment.

After treatment for GCT, you will have regular follow-up appointments for several years. You should receive a follow-up schedule from your clinical nurse specialist.

The usual practice will include:

• A chance to discuss symptoms
• Looking for any signs of the tumour returning (this may include x-rays or an MRI if required)
• Looking for any secondary tumours occurring in the lungs (this may include a chest x-ray or a CT scan)

GCT is known to come back in the same area of the original tumour. This is called a local recurrence. If the tumour does reappear, it is important to get treated quickly. This could involve further surgery or Denosumab treatment.

You can check for recurrences yourself. The most common sign of a GCT recurrence is pain. You may also find a new swelling or a lump. If you are worried about your tumour returning, contact your doctor or nurse. They may decide to bring forward the date of your follow up appointment to investigate your concerns.

What if my GCT spreads to another part of my body?

A recurrence of GCT can be accompanied by GCT cells spreading to other parts of the body. This is known as metastasis, which occurs in less than 10% of cases. It is most likely to spread to the lungs, particulraly in patients who are high-risk who are first diagnosed with an existing fracture. Treatment can include surgery to remove the tumours and/or Denosumab.

In a very small number of cases (less than 1%), where GCT becomes malignant (cancerous) and more aggressive, there are treatment options which your doctor will discuss with you.