- Design
- Retrospective registry cohort with inverse probability weighted counterfactual modelling
- Population
- 58,184 patients with HPV-negative head and neck squamous cell carcinoma, US National Cancer Database
- Primary outcome
- Five-year overall survival
- Effect
- Observed 58% vs predicted 58% with universal radiotherapy within 42 days
Using the US National Cancer Database, researchers studied 58,184 people with HPV-negative head and neck squamous cell carcinoma who received postoperative radiotherapy. They used inverse probability weighting to estimate survival in a counterfactual world where every patient started within 42 days of surgery.
Observed five-year overall survival was 58%, and predicted survival with universal timely radiotherapy was also 58%. No subgroup showed a predicted benefit whose interval excluded no effect; Black patients were predicted to do slightly worse.
This is a modelling study and does not show that delay is harmless for an individual patient. The six-week target in quality measures and guidelines has not changed. Its message is that, at population level, simply hitting the target may not move survival without addressing why patients are delayed.
- Keep aiming to start postoperative radiotherapy within six weeks; this study does not change that target.
- Look at the causes of delay — wound healing, dental work, referral and capacity — rather than the date alone.
- Arrange pre-radiotherapy dental assessment before surgery to avoid avoidable delay.
- Interpret population models cautiously when counselling an individual patient.
Why it matters
It questions whether a widely used quality target, on its own, changes survival.
Don't overread it
A counterfactual model from registry data cannot show that delay is safe for any one patient.
The statistics, in plain English
Observed and predicted survival both at 58% means the model found no difference. Counterfactual modelling depends on the confounders it adjusts for; unmeasured reasons for delay could hide a real effect.
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