Immunotherapy Before Surgery: A New Hope for Colorectal Cancer Patients

A groundbreaking UK-led clinical trial has revealed that a short course of immunotherapy given before surgery can keep certain colorectal cancer patients cancer-free for nearly three years. This approach, which uses the drug pembrolizumab for just nine weeks before tumor removal, challenges the traditional sequence of surgery followed by months of chemotherapy. The results have stunned oncologists and offer new hope for patients with a specific type of colorectal cancer. Below, we answer key questions about this promising development.

1. What is the new breakthrough in colorectal cancer treatment?

The breakthrough involves administering a short burst of immunotherapy before surgery for a specific subset of colorectal cancer. In a UK-led trial, patients received just nine weeks of the immunotherapy drug pembrolizumab (Keytruda) prior to having their tumors surgically removed. The trial found that these patients remained cancer-free nearly three years later, a striking outcome that could transform standard care for this type of cancer. This pre-surgical immunotherapy appears to prime the immune system to attack the tumor more effectively, leading to durable remissions without the need for prolonged chemotherapy afterward.

2. How long did patients remain cancer-free after this treatment?

Patients in the trial who received the nine-week course of pembrolizumab before surgery have remained cancer-free for almost three years after their treatment. This is a remarkable result, especially considering that many patients with this type of colorectal cancer would typically face a higher risk of recurrence after standard therapies. The near-three-year milestone suggests that the immune system may have been trained to recognize and eliminate any residual cancer cells, providing long-term protection. Follow-up is ongoing, but the current data are already challenging conventional wisdom about the best timing for immunotherapy in colorectal cancer.

3. How does this approach differ from the standard treatment?

The standard approach for colorectal cancer is surgery first, followed by months of adjuvant chemotherapy to mop up any remaining cancer cells. In contrast, this new strategy flips the order: patients receive a short course of immunotherapy before surgery. This neoadjuvant immunotherapy is given for only nine weeks, whereas post-surgery chemotherapy can last four to six months and often causes significant side effects. The trial results show that the pre-surgery approach not only spares patients from prolonged chemo but also leads to similar or better cancer-free survival rates. If confirmed in larger studies, this could become the new standard for eligible patients.

4. What type of immunotherapy was used and for how long?

The immunotherapy used was pembrolizumab, a PD-1 inhibitor that helps the immune system detect and attack cancer cells. Patients received this drug for a total of nine weeks before undergoing surgery. Pembrolizumab is already approved for several cancers, including those with high microsatellite instability (MSI-H) or mismatch repair deficiency (dMMR)—likely the specific colorectal cancer subset in this trial. The short nine-week duration is key: it is enough to unleash a powerful immune response but short enough to avoid the long-term side effects of continuous immunotherapy. This “short burst” strategy appears both effective and tolerable.

5. Why is this outcome considered surprising?

Oncologists expected some benefit from pre-surgery immunotherapy, but the magnitude of the result—nearly three years cancer-free for most patients—was unexpected. Historically, giving immunotherapy only nine weeks before surgery was thought to be too brief to produce lasting effects. Moreover, the standard sequence (surgery first, then chemo) has been dogma for decades. The trial challenges that dogma by showing that flipping the order can yield better outcomes. Several patients in the trial even had a complete pathological response, meaning no cancer cells were found in the surgical specimen. These surprises are now driving excitement for larger, confirmatory studies.

6. What are the implications for future colorectal cancer care?

If larger trials confirm these results, pre-surgery immunotherapy could become the new standard of care for patients with MSI-H/dMMR colorectal cancer. It would spare many from intensive chemotherapy and its side effects, while improving the chances of long-term remission. The approach may also be tested for other cancers with similar immune characteristics. Additionally, this trial underscores the value of neoadjuvant immunotherapy—giving immune agents before surgery to take advantage of an intact tumor as a vaccine. Ultimately, this breakthrough could lead to shorter, more effective treatments that preserve quality of life for thousands of patients worldwid.