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An immunotherapy drug that “melts” tumors dramatically increases the chances of bowel cancer being cured and could even replace the need for surgery, doctors have said.
Pembrolizumab targets and blocks a specific protein on the surface of immune cells, which then seek out and destroy cancer cells.
Giving the drug before surgery instead of chemotherapy led to a huge increase in patients 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 Hospital London, Christie NHS Foundation Manchester, St James’s University Hospital Leeds, University Hospital Southampton and the University of Glasgow.
Prof Mark Saunders, consultant clinical oncologist at Christie, said the trial results were “really very exciting”.
“Immunotherapy before surgery can be a ‘game changer’ for these patients with this type of cancer.” Not only is the outcome better, but it spares patients 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 annually, according to the World Health Organization.
In the study, funded by Merck Sharp and Dohme and sponsored by University College London, researchers recruited 32 patients with stage 2 or 3 bowel cancer and a certain genetic profile (MMR deficiency/MSI-High bowel cancer) from five UK hospitals.
About 15% of patients with stage 2 or 3 bowel cancer have this specific genetic makeup.
Patients were given nine weeks of pembrolizumab, also known as Keytruda, before surgery instead of the usual treatment of chemotherapy and surgery, then monitored over time.
The results showed that 59% of patients had no signs of cancer after treatment with pembrolizumab, and the cancer in the remaining 41% of patients was removed during surgery.
All patients in the study 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 study will also assess overall survival and recurrence rates.
The approach also means patients do not need post-operative chemotherapy, which has side effects and is difficult to endure.
Dr Kai-Keen Shiu, principal investigator of the trial and consultant medical oncologist at UCLH, said: “Our results show that pembrolizumab is a safe and highly effective treatment for improving outcomes in patients with high-risk bowel cancer, increasing the chances of curing the disease at an early stage.”
Shiu cautioned that the team would have to wait to see if patients in the study remained cancer-free for a longer period of time, but said the initial indications were “extremely positive.”
“Immunotherapy can make tumors disappear before surgery. If you melt the cancer before surgery, you usually triple your chances of survival,” Shiu added. “If patients have a complete response to pembrolizumab, it can triple your chance of survival.
“Patients also don’t need chemotherapy afterwards, so they avoid all those side effects.”
Dr Marnix Jansen, Clinical Scientist at UCL Crab Institute, said more work needs to be done to evaluate pembrolizumab before it can be considered a standard treatment. “But given the quality of the results of this trial, I think it’s possible we’ll see it in the clinic within a few years if subsequent trials are just as successful.”
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