The study followed 32 patients with stage two or three bowel cancer who were MMR deficient /MSI-High bowel cancer (aka mismatch repair cancer syndrome) which means they have a high level of deficient cells with a large number of genetic mutations.
The patients were given nine weeks of pembrolizumab, also known as Keytruda, instead of chemotherapy ahead of their surgery. At the end of the nine weeks, 59% of the patients had no cancer remaining in their body and the other 41% had their remaining cancer successfully removed.
Typically, in bowel cancer patients with MMR deficient/MSI-High bowel cancer, less than 5% of patients show no signs of cancer after surgery.
Pembrolizumab blocks a specific protein on the surface of cells, compelling them to seek out and destroy cancer cells. The patients also did not have to suffer through post-op chemotherapy, which can be extremely taxing on patients’ bodies.
The study was led by the University of College London, University College London Hospital, the Christie National Health Service Foundation Trust in Manchester, St. James’ University Hospital in Leeds, University Hospital Southampton and the University of Glasgow.
“Immunotherapy [like pembrolizumab] can make tumors disappear before surgery. If you melt the cancer away before surgery you normally triple survival chances,” Dr. Kai-Keen Shiu, the trial’s chief investigator and a consultant medical oncologist at University College London Hospital, explained. “If patients have a complete response to pembrolizumab it can triple your chance of survival.”
Pembrolizumab is already used to treat a variety of different cancers, including lung, head, neck, stomach and cervical cancer, along with certain types of breast cancer, Hodgkin's lymphoma and melanoma.
The trial will continue over the next few years and will assess the patients’ relapse and overall survival rates.
The study was presented at the world’s largest cancer conference the American Society of Clinical Oncology