Immunotherapy Before Surgery May Reduce Colon Cancer Recurrence

Why It Matters

If validated, pre‑operative pembrolizumab could dramatically lower recurrence and spare 10‑15% of colon‑cancer patients the toxicity of adjuvant chemotherapy, reshaping standard care.

Key Takeaways

• 9‑week pembrolizumab before surgery eliminated recurrences in 32 patients
• 59% achieved pathologic complete response; all remained disease‑free at 33 months
• ctDNA clearance predicted response, enabling personalized treatment decisions
• Could replace or reduce post‑operative chemotherapy for MMR‑deficient/MSI‑high tumors

Pulse Analysis

Colorectal cancer remains the world’s third most common malignancy and the second leading cause of cancer death, with surgery followed by months of chemotherapy the current backbone of treatment. However, the MMR‑deficient/MSI‑high subtype—representing roughly 10‑15% of stage II‑III cases—shows limited benefit from conventional chemotherapy, prompting oncologists to explore immune‑based strategies that exploit the tumors’ high neoantigen load. The emergence of checkpoint inhibitors, particularly pembrolizumab, has already transformed management of metastatic MSI‑high disease, but their role in earlier stages has been less clear.

The NEOPRISM‑CRC phase II study administered a short, nine‑week course of pembrolizumab before definitive surgery in 32 patients with high‑risk stage II or stage III disease. Remarkably, 59% of participants achieved a pathologic complete response, and after a median 33‑month follow‑up no patient experienced disease recurrence—a stark contrast to the roughly 25% relapse rate seen with standard surgery plus adjuvant chemotherapy. Crucially, the trial incorporated ultra‑sensitive ctDNA assays; patients whose blood‑based tumor DNA vanished after immunotherapy were the ones who remained cancer‑free, offering a real‑time biomarker to guide treatment intensity.

If larger, randomized trials confirm these early signals, the oncology community could see a paradigm shift: pre‑operative immunotherapy may become the preferred neoadjuvant approach for MSI‑high colon cancers, potentially eliminating the need for post‑operative chemotherapy and reducing treatment‑related toxicity. Such a change would not only improve patient quality of life but also lower healthcare costs associated with prolonged chemotherapy regimens. Moreover, the integration of ctDNA monitoring could usher in a new era of precision oncology, where therapy is dynamically adjusted based on molecular response rather than static staging alone.