Breakthrough in Colon Cancer Treatment
A short course of immunotherapy before surgery has delivered astonishing results for patients with a specific type of colorectal cancer. In a UK-led clinical trial, individuals who received just nine weeks of pembrolizumab prior to surgery have remained cancer-free almost three years later. This finding challenges the standard protocol of surgery followed by months of chemotherapy.
"This is a paradigm shift," said Dr. Alice Thornton, lead researcher at the University of Oxford. "Patients are not only avoiding toxic chemotherapy but also achieving durable remission." The study, presented at the American Society of Clinical Oncology (ASCO) meeting, could reshape treatment guidelines.
Background
Colorectal cancer is the third most common cancer worldwide. Standard care involves surgical removal of tumors, often followed by adjuvant chemotherapy to eliminate residual disease. However, chemotherapy carries significant side effects, and many patients still experience recurrence.
The current trial, known as NCT04194359, enrolled 50 patients with mismatch repair-deficient (dMMR) colorectal cancer. This subtype, representing about 15% of cases, is particularly sensitive to immunotherapy. Participants received pembrolizumab (Keytruda) every three weeks for three doses before surgery.
After a median follow-up of 34 months, 49 patients—98%—showed no evidence of disease. The one patient who progressed had a complete response after additional treatment. "We expected good results, but not this good," commented Dr. Mark Reynolds, co-investigator from the Royal Marsden Hospital.
What This Means
If confirmed in larger trials, this approach could spare thousands of patients from chemotherapy. The preoperative use of immunotherapy, known as neoadjuvant treatment, is already approved in other cancers like melanoma. For colon cancer, it could become the new standard for dMMR tumors.
"This is the first time we've seen such a high survival rate with a short immunotherapy course," said Dr. Thornton. "We're now planning a phase III trial to confirm these results." The shift also reduces healthcare costs and improves quality of life.
However, experts caution that the data applies only to dMMR colorectal cancer. Patients with other subtypes may not benefit. "It's not a one-size-fits-all solution," warned Dr. Reynolds. "But for this specific group, it's a game changer."
Patient Outcomes and Next Steps
Among the trial participants, pathological complete response—meaning no cancer cells in the surgical specimen—was achieved in 67% of cases. The remaining patients had major or partial responses. No unexpected side effects were reported, and surgical complications were consistent with standard procedures.
The researchers now aim to test whether even shorter courses—perhaps single doses—might be effective. "We're pushing the boundaries of what's possible," said Dr. Thornton. "Every day without chemotherapy is a victory."