Article review: Long term results of Keynote 412- supports lack of clear benefit by immunotherapy to CRT in H&N cancers

 Five Key Takeaways

1. Pembrolizumab added to CRT improved 6‑year event‑free survival (HR 0.79) but missed clear OS significance.
2. Benefit concentrated in PD‑L1–positive tumors.
3. Toxicity remained manageable—no major safety surprises.
4. Results don’t yet justify routine NHS use but validate immunotherapy‑CRT feasibility.

For now, stick with cisplatin‑CRT as standard; consider pembrolizumab‑CRT only in selected PD‑L1–positive, trial‑eligible patients

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Pembrolizumab + Chemoradiotherapy in Head & Neck Cancer: 6-Year Update from KEYNOTE‑412

Study: KEYNOTE‑412: Pembrolizumab + Cisplatin–Radiotherapy vs Standard CRT in Unresected, Locally Advanced HNSCC
Authors: Harrington KJ, Rischin D, Ghi MG, et al.
Journal: Journal of Clinical Oncology (ASCO 2025 supplement)
Date: May 31, 2025
DOI: 10.1200/JCO.2025.43.16_suppl.6013; https://ascopubs.org/doi/pdf/10.1200/JCO.2025.43.16_suppl.6013

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The Big Picture

If you treat head and neck cancer, you’ve probably been asking whether immunotherapy can make a meaningful difference when added to chemoradiation.
KEYNOTE‑412, a large global phase 3 trial, followed more than 800 patients with unresected, locally advanced head and neck squamous cell carcinoma (HNSCC) for over six years.

The goal: determine whether adding pembrolizumab to standard high‑dose cisplatin and radiotherapy could improve event‑free survival (EFS) versus chemoradiation alone.

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Study at a Glance

• Design: Double‑blind, randomised phase 3 (804 patients, 1:1)
• Treatment: 70 Gy IMRT + cisplatin (100 mg/m² q3w ×3) ± pembrolizumab (17 total cycles)
• Population: Unresected stage III–IV HNSCC (larynx, hypopharynx, oral cavity, p16‑negative oropharynx, or high‑risk p16+ disease)
• Follow‑up: Median 74.4 months

This was a well‑run, double‑blind trial—the gold standard—with excellent follow‑up.
A small caveat: the first analysis years ago was technically negative, and these are updated long‑term results showing clearer trends.

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Headline Results

• Event‑Free Survival (EFS): HR 0.79 (95% CI 0.65 – 0.96)
  → About a 21% relative risk reduction in recurrence, metastasis, second primary, or death.
  → EFS at ~6 years: 53.7% (pembro) vs 46.0% (placebo) — roughly 8% absolute benefit.
• Overall Survival (OS): Favors pembrolizumab but not statistically significant yet.
• Benefit strongest in: PD‑L1–positive tumors (CPS ≥ 1 or ≥ 10).
• Toxicity: Slight rise in immune‑related events (thyroiditis, hepatitis, mild pneumonitis), but serious toxicities were similar between arms.

In plain English: pembrolizumab + CRT modestly improved EFS, looked safe, but didn’t prove a clear survival benefit.

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What It Means

This is the first chemoradiotherapy–immunotherapy trial in head and neck cancer to show a durable, statistically credible EFS benefit—though not quite strong enough to change global guidelines overnight.

It fits the emerging pattern seen with immunotherapy across HNSCC:

• Works best with PD‑L1–positive disease.
• Benefit is more modest when given concurrently with CRT.
• Peri‑operative or adjuvant timing (e.g., KEYNOTE‑689) may be more effective.

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UK NHS Context

For NHS practice:

• Cisplatin‑based chemoradiotherapy remains the gold standard.
• Pembrolizumab‑CRT may be considered only in high‑risk, PD‑L1–positive cases, ideally within a trial.
• NICE would likely deem this combination not yet cost‑effective given modest benefit and long treatment duration (17 doses!).
• MDTs should continue exploring trial enrolment for peri‑operative or biomarker‑driven immunotherapy strategies.

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