Clinical trial results show that pembrolizumab, an immunotherapy drug used to treat multiple types of cancer, can dramatically improve outcomes for patients with colorectal cancer and may eliminate the need for surgery. Pembrolizumab is a monoclonal antibody that binds to the PD-1 protein on the surface of T cells. By blocking PD-1, pembrolizumab helps immune cells detect and attack cancer cells.
Promising Trial Results
The drug was evaluated in a clinical trial led by University College London in collaboration with several other institutions in the UK. The findings, which are interim results from the NEOPRISM-CRC Phase II clinical trial, were presented at the 2024 American Society of Clinical Oncology (ASCO) Annual Meeting.
The trial involved 32 patients with stage two or three colorectal cancer with a particular genetic profile (mismatch repair-deficient/microsatellite instability-high). About 10 to 15 percent of patients with stage two or three colorectal cancer have this disease subtype. The study participants received pembrolizumab for nine weeks before surgery instead of the usual pre-operative chemotherapy treatment.
The results were impressive. “Immunotherapy prior to surgery could well become a ‘game-changer’ for these patients,” said Mark Saunders, part of the research team and a consultant clinical oncologist at the Christie NHS Foundation Trust in Manchester, UK. “Not only is the outcome better, but it saves patients from having more conventional chemotherapy, which often has more side effects. In the future, immunotherapy may even replace the need for surgery.”
Impact on Colon Cancer Treatment
Colorectal cancer is the third most common cancer and the second leading cause of cancer-related deaths globally. The World Health Organization estimates that there were more than 1.9 million new cases in 2020 and more than 930,000 colon cancer-related deaths worldwide. The disease most commonly occurs in older patients, but in recent decades, rates have been rising among people age 55 and younger.
Early detection of colon cancer improves the chances of survival. About 90 percent of patients treated for stage one colon cancer survive for five years or more, but specific sub-types of cancer don’t respond as well to treatment and are more likely to recur. Five-year survival declines to 65 percent in stage three and 10 percent in stage four colorectal cancer.
The promising results of this trial could change the treatment landscape for many patients. Kai-Keen Shiu, the trial’s chief investigator and a consultant medical oncologist at University College Hospital in London, said in a statement, “Our results indicate that pembrolizumab is a safe and highly effective treatment to improve outcomes in patients with high-risk [colorectal] cancer, 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.”
Cancer Free
After treatment with pembrolizumab, 59 percent of patients showed no signs of cancer. The remaining 41 percent of patients had their cancer removed during surgery. All 32 patients remained cancer-free months later. This is a significant improvement compared to the results of the standard chemotherapy treatment for patients with this genetic profile, which show that less than 5 percent of patients are cancer-free after surgery.
Moving Forward
While the initial results are promising, the researchers cautioned that further follow-up is needed. They will continue to evaluate study participants’ overall survival and relapse rates over the next five years. According to senior study author Marnix Jansen, a clinician scientist and consultant histopathologist at the University College London Cancer Institute, “More work needs to be done to assess pembrolizumab before it could be considered standard treatment.” However, he expressed optimism about the drug’s future impact if subsequent trials have similar success.
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