Radiomics validation crisis: external validation set obsession is only half the problem

Radiomics model validation is in crisis: the field’s overemphasis on external validation sets overlooks undertraining, which is equally critical. A balanced approach to both is needed.

• Perspective article argues that the “cult of the external validation set” distracts from the pervasive issue of undertraining in radiomics.
• Highlights two interconnected parts of the validation crisis: external validation fixation and undertraining, both undermining model reliability.
• No primary data; a commentary on methodological shortcomings in radiomics research.

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