June 23, 2024


A “gamechanger” immunotherapy drug that “melts away” tumors dramatically increases the chances of curing bowel cancer and could even replace the need for surgery, doctors said.

Pembrolizumab targets and blocks a specific protein on the surface of immune cells that then seeks out and destroys cancer cells.

Giving the drug before surgery instead of chemotherapy led to a huge increase in patients being declared cancer-free, a clinical trial found. The results were presented at the annual meeting of the American Society of Clinical Oncology (ASCO), the world’s largest cancer conference.

The study was led by University College London, University College London Hospital, the Christie NHS Foundation Trust in Manchester, St James’s University Hospital in Leeds, University Hospital Southampton and the University of Glasgow.

Prof Mark Saunders, a consultant clinical oncologist at the Christie, said the trial results were “really very exciting”.

“Immunotherapy before surgery could very well become a ‘game changer’ for these patients with this type of cancer. Not only is the outcome better, but it spares patients from more conventional chemotherapy, which often has more side effects. In the future, immunotherapy may even replace the need for surgery.”

Bowel cancer is the second leading cause of cancer-related deaths worldwide. There are more than 1.9 million new cases and more than 900,000 deaths per year, according to the World Health Organization.

In the trial, funded by Merck Sharp and Dohme and sponsored by University College London, researchers recruited 32 patients with stage two or three bowel cancer and a certain genetic profile (MMR-deficient/MSI-High bowel cancer) from five hospitals in the UK .

About 15% of patients with stage two or three bowel cancer have this particular genetic makeup.

Patients were given nine weeks of pembrolizumab, also known as Keytruda, before surgery instead of the usual treatment of chemotherapy and surgery, and then monitored over time.

Results show 59% of patients had no signs of cancer after treatment with pembrolizumab, with any cancer in the remaining 41% of patients removed during surgery.

All the patients in the trial were cancer-free after treatment. When standard chemotherapy was given to patients with this genetic profile, less than 5% had no signs of cancer after surgery, UCL said.

Over the next few years, the trial will also determine overall survival and relapse rates.

The approach also meant that patients did not need post-operative chemotherapy, which has side effects and is difficult to tolerate.

Dr Kai-Keen Shiu, the trial’s principal investigator and a consultant medical oncologist at UCLH, said: “Our results suggest that pembrolizumab is a safe and highly effective treatment for improving outcomes in patients with high-risk bowel cancer, which the increase the chances of cure at an early stage.”

Shiu cautioned that the team will have to wait to see if the patients in the trial remain cancer-free over a longer period of time, but said the initial indications were “extremely positive”.

“Immunotherapy can make tumors disappear before surgery. If you melt away the cancer before surgery, you usually triple the chances of survival,” added Shiu. “If patients have a complete response to pembrolizumab, it can triple your chance of survival.

“Patients also don’t need any chemotherapy, so they avoid all those side effects.”

Dr Marnix Jansen, a clinical scientist at UCL Cancer Institute, said more work needs to be done to assess pembrolizumab before it can be considered standard treatment. “But given the quality of the outcomes in this trial, I think it’s possible that we could see it in the clinic within a few years if subsequent trials are equally successful.”



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