Bowel cancer patients could be spared from chemotherapy thanks to a blood test that can identify whether surgery alone will tackle their tumour.

Currently, most bowel cancer sufferers are offered both treatments in a bid to stop remnants of the disease from spreading again after surgery. But studies show about half of these patients could be cured with surgery alone.

It means some 16,000 people a year unnecessarily endure the gruelling side effects of chemo, such as nausea, fatigue, infections, hair loss and permanent nerve damage.

Now oncologists at The Royal Marsden NHS Foundation Trust are trialling a blood test that predicts the likelihood that cancer will return after surgery by detecting tiny fragments of tumour DNA.

Dame Deborah James, pictured, underwent chemotherapy as part of her treatment for bowel cancer 

More than 40,000 Britons are diagnosed with bowel cancer every year. It is the second-biggest cancer killer, after lung cancer, largely because many cases are diagnosed at a late stage when it has spread to other parts of the body

Research shows that patients who have the DNA in their blood – called circulating tumour DNA – are far more likely to relapse within two years, and should therefore also undergo chemotherapy. Studies have also shown that the DNA can be spotted earlier than tumour growth can be detected by scans.

‘We have a big problem with over-treating patients,’ says Professor Lawrence Young, an expert in molecular oncology and director of Warwick University’s Cancer Research Centre.

‘As soon as someone is diagnosed, we remove the tumour with surgery, but there are big questions about whether to give chemotherapy. Most patients are given a concoction of nasty chemo drugs just in case – but for a lot of patients it’s unnecessary.

‘These types of blood tests will revolutionise treatment, allowing doctors to be confident in recommending against chemo.’

Bowel cancer campaigner and TV presenter Dame Deborah James, who died last June, graphically documented her own battles with what she called ‘vicious chemotherapy’.

NHS hospitals have already trialled the blood test in lung and skin cancers and found it to be highly accurate in spotting those patients most likely to relapse.

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More than 40,000 Britons are diagnosed with bowel cancer every year. It is the second-biggest cancer killer, after lung cancer, largely because many cases are diagnosed at a late stage when it has spread to other parts of the body.

‘Unfortunately, once bowel cancer is in the blood, it can quickly spread to the liver, where it multiplies rapidly,’ says Prof Young. Doctors therefore do all they can to prevent this, which usually involves a combination of potent drugs.

‘The standard treatment is a daily tablet called capecitabine and regular infusions of a stronger medicine called oxaliplatin,’ says Dr Naureen Starling, consultant oncologist at the Royal Marsden and co-lead on the trial.

‘But in four out of ten patients, oxaliplatin can cause debilitating, long-term nerve damage, so we may use tablets alone in elderly or vulnerable patients.’

Royal Marsden experts are offering 800 patients the new blood test after surgery, as part of a trial dubbed TRACC. If tumour DNA is not detected, patients will be given either a weaker form of chemotherapy or none at all

‘Patients who would otherwise have just been given the tablet will have no drug, and those who would have had the combination just get the tablet,’ says Dr Starling.

Dr Starling and her team are now working on an economic analysis for NHS drug watchdog, the National Institute for Health and Care Excellence (NICE).

She adds: ‘We think it will be value for money, considering the costs saved by sparing thousands from chemotherapy.’

One patient to benefit is 52-year-old Ben Cooke, from London. The father-of-two was diagnosed with bowel cancer in September and underwent surgery to remove part of his colon.

Within a few weeks he was offered the chance to take part in the TRACC trial. His results for circulating tumour DNA were negative, so doctors recommended a less potent form of chemotherapy.

Ben, who finished his treatment last month, said: ‘Since starting treatment I’ve felt absolutely fine and I haven’t had to take a day off work, which is amazing.

‘Conventional chemo would put me at risk of nerve damage in my hands, which could affect my ability to do my job, so I’m thankful I’m not at risk of these side effects.’