Shrinking a tumour with ­chemotherapy before surgery has long been established as leading to better results. Well, immunotherapy before the op can do even better. Researchers have shown that significantly more patients with a certain genetic profile are cancer free after surgery.

The clinical trial was assessing whether an immunotherapy drug (pembrolizumab) can improve outcomes for patients with stage two or stage three of a particular bowel cancer. It was orchestrated by a ­collaboration between UCLH, Christie’s Hospital in Manchester, St James’s Hospital in Leeds, and University Hospitals in Southampton and Glasgow.

Bowel cancer is the fourth most common cancer in the UK, with around 42,900 cases a year.

Although still predominantly a cancer that affects older people, cases among the under-50s have been increasing in recent years.

Like many cancers, if bowel cancer is caught early the chances of a ­positive outcome are high. Nine in 10 patients treated for stage one bowel cancer survive for five years or more, but five-year survival falls to 65% in stage three and 10% in stage four.

In this trial, researchers recruited 32 patients with stage two or three bowel cancer from five hospitals across the UK. Around 10-15% of patients with stage two or three bowel cancer have a particular genetic make-up, which represents around 2,000-3,000 cases per year in the UK. These patients were given nine weeks of ­pembrolizumab prior to surgery instead of the usual treatment of chemotherapy and surgery, then monitored over time.

The results were quite amazing, as 59% of patients had no signs of cancer after treatment with pembrolizumab, with any cancer in the remaining 41% of patients being removed during surgery. All the patients in the trial were cancer-free after treatment and are still cancer-free many months later. Furthermore, they had no need for any post-operative chemotherapy, which has side effects and is tough to endure.

When standard conventional ­chemotherapy is given to patients with this genetic profile, less than 5% have no signs of cancer after surgery.

Dr Kai-Keen Shiu, Chief Investigator from UCLH, said: “Our results indicate that ­pembrolizumab is a safe and highly effective treatment to improve outcomes in patients with high-risk bowel cancers, increasing the chances of curing the disease at an early stage.

“We need to wait to see whether the patients in our trial remain cancer-free over a longer period of time, but initial indications are extremely positive.”

Professor Mark Saunders, a Consultant Clinical Oncologist at The Christie, added: “In the future, immunotherapy may even replace the need for surgery.

“However, more trials are needed to confirm these exciting early results.”