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28 January 2020

By Dr Wendy Winnall - Scientific writer for PCFA.

Prostate tumours that have spread to the bones cause pain and have a major impact on quality-of-life. They can also lead to serious issues such as spinal compression. New research from the UK has addressed the best way to treat and prevent spinal compression using radiotherapy for men with prostate cancer.

Prostate tumours growing in bones

Tumours that have spread to the bones cause a lot of misery for men with prostate cancer. They cause discomfort and pain, increasing the need for serious pain relief drugs. Bone tumours reduce mobility and the ability to perform physical tasks. Bone tumours also increase the risk of broken bones.

A serious condition caused by bone tumours is called spinal compression. You may see this referred to as metastatic spinal cord compression. During spinal compression a tumour is pressing on or near the spinal cord. This causes pain and can damage the spinal cord if left untreated. Fortunately this condition is relatively rare. Treating spinal compression quickly is very important for preventing permanent damage to the spine. If left untreated, spinal compression can cause permanent nerve damage and paralysis.

A man with metastatic prostate cancer experiencing strong pain in his spine should seek medical advice very quickly. Treatments for spinal cord compression include pain relief, anti-inflammatory drugs, radiotherapy and sometimes surgery.

Preventing and treating skeletal events

Bisphosphonates are a family of drugs used to treat prostate cancer that has spread to the bones. Bisphosphonates work by slowing down bone re-absorption, allowing bone-forming cells time to rebuild normal bone. This protects the bones from being weakened. The main reason these drugs are administered is to minimise skeletal-related events (including bone pain, spinal compression, fracture, and the need for surgery or radiation). Bisphosphonates currently used in Australia are Zoledronic acid (Aclasta) and Denosumab (Xgeva).

Most patients with spinal compression receive radiotherapy. The radiation beams are directed at the tumour that is pressing on the spine. Radiotherapy damages the tumour, shrinking its size, and hopefully stopping it from damaging the spinal cord.

Research to improve radiotherapy for spinal compression

A clinical trial involving over 600 people has been conducted in the UK with the aim of improving radiotherapy for people with metastatic spinal cord compression. The study was run by a group of clinician/researchers from many different cancer clinics around the UK. Radiotherapy for spinal compression is commonly delivered in 5 to 10 treatment sessions. The aim of this new study was to ask whether radiotherapy could be effectively delivered in one session at a high dose.

Delivering radiotherapy in one session for men with prostate cancer should be beneficial. Men with pain and limited mobility would benefit from fewer trips to the clinic. Particularly in Australia, where some patients may need to travel long distances for their radiotherapy, one visit would be optimal. One treatment will also reduce costs for patients and for the healthcare system.

People joining the UK trial had either prostate cancer, lung cancer or breast cancer. Each of these cancers can spread to the bones and spinal cord. 41% of the people joining the trial were men with prostate cancer. Half the people in the trial received radiation in a single dose. The other half received their radiation in 5 doses over 5 days. The trial was designed to ask whether the single dose was as good as the 5 day doses.

To assess how well the treatment worked, the researchers used a measure called ambulatory status. This is a measure of how well people were able to walk around. They measured this on a scale where the best result was being able to walk without help and the worst result was not being able to move their leg muscles. Ambulatory status was measured 1 week after treatment, then after 4 weeks, 8 weeks, 12 weeks and 1 year. Unfortunately many of the people who volunteered for the trial did not live long enough for the 1-year assessment.

69.3% of people in the single-dose group recovered good mobility by 8 weeks after treatment. This was a little less than the 72.7% with good mobility after receiving 5 treatments over 5 days. 28% of people had lost mobility by 8 weeks after receiving the single dose, compared to 23% who received the 5 doses. These results showed that the one dose was similar, but not quite as good as the 5 doses.

Radiotherapy for spinal compression lead to some side effects. These included loss of bladder control and loss of bowel control. There appeared to be a greater risk of bladder problems in people who had the single dose of radiotherapy. The researchers predicted that 5 doses might be better for people whose spinal tumours were close to the bladder.

The conclusion from this study was that the single dose did not quite meet the criteria for being as good as 5 doses. It therefore seems unlikely that the one dose will replace the 5 or more doses usually given. However, despite not meeting the criteria set at the start of the trial, the differences between outcomes from the two treatments were small.

This clinical trial is an example of the continual process of improvement that is going on around the world. By testing and comparing new ways of delivering cancer treatments, researchers can optimise the care that patients receive. In the absence of major breakthroughs, numerous small improvements in medicine and treatments can improve survival times and quality-of-life for the people living with metastatic cancer.

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