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NNT Calculation — SCE Medical Oncology MCQ

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EasyClinical Trials & StatisticsNNT CalculationSCE Medical Oncology

A researcher explains the concept of 'number needed to treat' (NNT) to a patient. A trial shows 5-year OS of 72% with drug A vs 65% with drug B. What is the NNT?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Approximately 14 — NNT = 1/ARR = 1/(72%-65%) = 1/0.07 = 14.3; meaning 14 patients must be treated with drug A instead of drug B to prevent 1 additional death at 5 years

NNT is calculated as 1/ARR (absolute risk reduction). Here, ARR = 72% - 65% = 7% = 0.07. NNT = 1/0.07 = 14.3, rounded to 14. This means 14 patients need to receive drug A instead of drug B for one additional patient to be alive at 5 years. NNT provides a clinically intuitive measure of treatment benefit that is more meaningful than relative risk reduction or hazard ratios alone. NNT should always be interpreted alongside: treatment duration, toxicity (NNH — number needed to harm), cost and patient preferences.

Reference: JRCPTB Curriculum; ESMO Statistics; Altman et al BMJ 1998