Discrimination, spectrum, and clinical utility: ICG lymphography drainage time in axillary staging

This Correspondence responds to the prospective study by Anuszkiewicz et al., which assessed dynamic indocyanine green (ICG) lymphography drainage time as a marker of axillary nodal burden. We raise three methodological points relevant to how the results should be read. First, the cohort included only patients selected for axillary lymph node dissection, so it represents a narrow, non-representative spectrum in which discrimination tends to be optimistic; the reported area under the curve of 0.995 was obtained without internal or external validation. Second, an ipsilateral-to-contralateral ratio may be more transportable than the absolute threshold that was used. Third, discrimination is not the same as clinical utility, which also depends on calibration and net benefit. We outline directions for validation and future study.