NEOPRISM-CRC vs KEYNOTE Trials in Colorectal Cancer (2026)

1. Core similarity: same drug, different strategy

Both programs use:

• Pembrolizumab (anti–PD-1 immunotherapy)

• In MSI-high / dMMR colorectal cancer

• Aiming to harness immune system tumor control

But they differ in a crucial way:

• KEYNOTE = mostly advanced/metastatic or adjuvant settings
• NEOPRISM = true neoadjuvant “pre-surgery immune priming” strategy.

2. KEYNOTE colorectal program (what it established)

🔹 KEYNOTE-177 (landmark trial)

KEYNOTE-177 Trial

Population:

• Metastatic MSI-high / dMMR colorectal cancer

Design:

• Pembrolizumab vs chemotherapy

Key results:

• Progression-free survival: ~16 vs ~8 months

• Higher response durability

• Lower toxicity than chemo

Key limitation:

• Majority of patients still have disease progression over time

• Not designed for “curative intent”

👉 Bottom line:
KEYNOTE-177 established pembrolizumab as first-line metastatic standard, not a cure strategy.

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🔹 KEYNOTE-016 / 164 / 158 (earlier proof-of-concept)

KEYNOTE-016 Trial

• Showed high response rates (~30–40%+ durable responses)

• Confirmed MSI-high tumors are highly immunotherapy sensitive

• But still in advanced disease settings

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🔹 KEYNOTE-868 / perioperative studies (emerging)

KEYNOTE-868 Trial

• Moving toward neoadjuvant / perioperative immunotherapy

• Still evolving, not yet definitive long-term relapse data.

Keytruda

Keytruda is the world's bestselling cancer drug by Merck & Co.
Company: Merck & Co.
2025 sales: $31.7 billion

Diseases: 

1. Melanoma, (KEYNOTE-006 and KEYNOTE-054 trials)*
   
2. Non-small cell lung cancer, (KEYNOTE-010, KEYNOTE-407, KEYNOTE-189, KEYNOTE 671 trials)
3. head and neck cancer, (KEYNOTE-012 and KEYNOTE-048)
4. kidney cancer (renal cell carcinoma), (KEYNOTE-426)
5. classical Hodgkin lymphoma, (KEYNOTE-204)
6. primary mediastinal large B-cell lymphoma, 
7. bladder cancer, (EV-302/KEYNOTE-A39) 
8. microsatellite instability-high or mismatch repair deficient cancers**
9. gastric cancer, 
10. esophageal cancer, 
11. cervical cancer, 
12. liver cancer, 
13. biliary tract cancer, 
14. Merkel cell carcinoma, 
15. endometrial cancer, 
16. tumor mutational burden-high cancer, 
17. cutaneous (skin) squamous cell carcinoma, 
18. Triple-negative breast cancer. (ASCENT-04/KEYNOTE-D19 Study)
19. Colorectal cancer (KEYNOTE-177, KEYNOTE-016 / 164 / 158)

*The name KEYNOTE is not an acronym but rather a code that identifies specific clinical trials for the immunotherapy drug Keytruda (pembrolizumab). Merck & Co., the manufacturer of Keytruda, assigns a unique KEYNOTE number to each clinical study to track research into the drug's effectiveness for different cancers and treatment regimens.

**Microsatellite Instability-High (MSI-H) or Mismatch Repair Deficient (dMMR) cancers are tumors with high mutation rates due to faulty DNA repair mechanisms. These cancers are highly immunogenic, making them exceptionally responsive to immunotherapy (checkpoint inhibitors) and typically carry a better prognosis in early stages. Most common in colorectal (15%), stomach, and endometrial cancers.

3. NEOPRISM-CRC (UCL study) — what is different?

Patients with a specific type of bowel cancer who were treated with a short course of immunotherapy before surgery instead of post-op chemotherapy have remained cancer-free after almost three years of follow-up, according to new results from the NEOPRISM-CRC clinical trial led by a team from UCL and UCLH.

The latest findings, presented at the American Association for Cancer Research (AACR) Annual Meeting 2026 in April, build on earlier results showing that nine weeks of pre-operative immunotherapy using the drug pembrolizumab led to major tumour shrinkage in patients with stage two or three bowel cancer.

The NEOPRISM-CRC trial saw 32 patients recruited with stage two or three bowel cancer and a certain genetic profile (MMR deficient/MSI-high bowel cancer) from five hospitals around the UK. Around 10-15% of patients with stage two or three bowel cancer have this particular genetic make-up, which represents around 2,000-3,000 cases per year in the UK.

NEOPRISM-CRC is an early-phase clinical trial in which patients with a specific genetic subtype of bowel cancer received short-course pre-surgery immunotherapy (pembrolizumab) instead of standard post-operative chemotherapy. After nearly 33 months of follow-up, the researchers report no cancer recurrences in the treated cohort. (University College London)

NEOPRISM-CRC Trial - Key design differences:

🔹 Timing

• NEOPRISM: immunotherapy BEFORE surgery (neoadjuvant)

• KEYNOTE (main): mostly AFTER relapse/metastatic or adjuvant

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🔹 Goal

• NEOPRISM: prevent recurrence entirely (“immune eradication window”)

• KEYNOTE: extend survival, delay progression

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🔹 Disease stage

• NEOPRISM: earlier-stage (Stage II–III, curative-intent surgery planned)

• KEYNOTE: largely metastatic or mixed populations

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🔹 Outcome signal

• NEOPRISM: reported 0 relapses at ~3 years in small cohort

• KEYNOTE: improved survival, but not zero relapse

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🧠 4. Why NEOPRISM may look “stronger” (but isn’t directly comparable)

The zero-relapse result sounds dramatic, but it reflects:

✔ 1. Earlier disease biology

• Less tumor burden

• More intact immune surveillance

✔ 2. Immune priming effect

Giving PD-1 blockade while tumor is still present may:

• Train immune system more effectively

• Generate long-lived T-cell memory

✔ 3. Strong selection bias overlap

Both programs focus on:

• MSI-high / dMMR tumors
  → already the most immunotherapy-responsive colorectal subtype.

5. Key differences in evidence strength

6. Interpretation in plain terms

KEYNOTE program tells us:

“Pembrolizumab works better than chemo in metastatic MSI-high colorectal cancer and extends life.”

NEOPRISM suggests:

“If you use immunotherapy earlier—before surgery—you might eliminate detectable relapse in selected patients.”

But critically:

• KEYNOTE is proven standard therapy
• NEOPRISM is promising but not yet practice-changing

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🔬 7. The real scientific evolution (2024–2026 trend)

These studies together show a progression:

Stage 1: Metastatic success (KEYNOTE-177)

→ immunotherapy works in advanced disease

Stage 2: Adjuvant exploration

→ trying to prevent recurrence after surgery

Stage 3: Neoadjuvant immunotherapy (NEOPRISM, others)

→ treating cancer as an immune training event before removal

Stage 4 (future direction)

→ “surgery de-escalation” or even “non-operative complete response management” in select cases

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🧾 Bottom line

• KEYNOTE trials = established proof that PD-1 blockade improves survival in MSI-high colorectal cancer, especially metastatic disease.

• NEOPRISM-CRC = early but provocative evidence that giving immunotherapy before surgery may dramatically reduce or possibly eliminate relapse in a small, highly selected group.