Statistically significant is not automatically worthwhile
ESMO-MCBS scores the size of benefit in studies that are already statistically positive. Its purpose is to distinguish a small, formal effect from one likely to matter to patients.
Written retrospectively and published on August 3, 2026.
Background reading, not clinical guidance. This describes published research; it is not a recommendation for any individual case, and the cited studies may have been superseded.
A p-value can say that an observed difference is unlikely to be due to chance under a statistical model. It does not say whether the difference is large enough to change a person’s experience, time without disease progression, or survival in a meaningful way.
ESMO created its Magnitude of Clinical Benefit Scale for that second question. It is applied to trials that have already met their formal positive criterion. The scale then considers relative effect, absolute gain, quality of life and toxicity, using different forms for different trial designs.
A positive trial can receive the lowest non-curative score
In the survival-based forms, a large-looking relative effect is not enough: the observed median gain must also clear a minimum threshold. This design intentionally downgrades statistically significant results with clinically trivial benefit.
For example, a pancreatic-cancer trial of gemcitabine plus erlotinib reported a statistically significant survival difference of about ten days. The example does not invalidate the trial; it illustrates why “significant” and “substantial” are separate claims.
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