Discordant marrow MRD and PET ‐ CT in myeloma: A four‐state language for joint reporting

Summary In a Nutshell, discordant bone marrow measurable residual disease (BM‐MRD) and positron emission tomography‐computed tomography (PET‐CT) assessments in multiple myeloma do not simply represent assay disagreement. They can provide clinically relevant information because the direction of discordance changes the interpretation of response: BM‐MRD‐negative/PET‐positive disease indicates PET‐visible disease outside the sampled marrow compartment, whereas BM‐MRD‐positive/PET‐negative disease reflects marrow persistence without PET‐visible disease. This distinction matters for defining deep response, interpreting MRD‐driven end‐points and designing studies of response‐adapted treatment. A four‐state language turns discordance from an ambiguous finding into a reportable response framework.