Blood test could spare cancer patients from unnecessary chemotherapy

Australian researchers have developed a new blood test that can separate cancer patients who need chemotherapy from those who can be spared the intense treatment.

Each year in Australia, more than 150,000 people are diagnosed with cancer, at a rate of over 400 per day. Many of these people will begin the long, expensive and physically demanding process of chemotherapy treatment.

For some, chemo is necessary and can’t be avoided, but for those more fortunate, removing the cancerous growth through surgery is all that’s needed for a full recovery.

The problem is that chemotherapy is still often used to ensure cancer hasn’t spread to other parts of the body through tiny cells called micrometastases. These tiny cancer particles don’t show up on regular scans, so chemo is used to eradicate any chance of them, even when it may not be necessary.

Read: Doctors obliterate cancer in new clinical trial

Now, in a ground-breaking collaboration, Melbourne’s Walter & Eliza Hall Institute (WEHI) and the Johns Hopkins Kimmel Cancer Centre in the US have developed a blood test that can accurately predict whether patients suffering from colon cancer will need chemotherapy or if it can be safely avoided.

More than 450 patients across 20 Australian hospitals took part in a clinical trial to see whether the test would be beneficial to cancer treatment decision-making.

The blood test assesses the level of circulating tumour DNA (ctDNA) – the genetic material released by the tiny metastases as they move through the body.

Read: Liver cancer can be treated if caught early enough

If high levels are detected, then spreading is likely and chemotherapy would be beneficial. But if they are below a certain background threshold, then the cancer likely hasn’t spread micrometastases and chemo can be avoided.

“Our trial has conclusively shown how the ctDNA blood test can be used to direct post-surgical therapy in stage II colon cancer and substantially reduce the number of patients treated with chemotherapy, without impacting the risk of cancer relapse,” says study co-author Dr Jeanne Tie.

“We found that when a patient’s blood test does not reveal ctDNA after colon surgery, the likelihood of micrometastases is very low and chemotherapy can be avoided as there are no tumour fragments left to kill.”

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More than 15,000 Australians are diagnosed with colon cancer each year, accounting for around 10 per cent of all cancer diagnoses. Chemotherapy is offered to all stage II colon cancer patients as a precaution, despite a majority not needing it.

“While chemotherapy can be essential and lifesaving, many patients are receiving the treatment and its associated toxicities without any benefit,” Dr Tie says.

“This ctDNA blood test could be used to spare around 600 Australians and over 100,000 people worldwide from unnecessary chemo treatments each year.”

Three clinical trials are underway to see whether this method can detect cancer spread in other types of cancers, including pancreatic and ovarian cancer.

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