This prospective single-arm trial evaluated [18F]FDG PET/MRI as a non-invasive post-treatment axillary staging tool in 68 node-positive breast cancer patients receiving primary systemic therapy (PST), comparing its performance to axillary ultrasound (A-US) against surgical pathology as the reference standard.
PET/MRI sensitivity was 53.3% and specificity 68.4% (PPV 57.1%, NPV 65.0%) for residual axillary disease in 30/68 (44.2%) patients with pathologically confirmed disease; performance did not significantly differ from A-US (p > 0.05). PPV was higher in luminal subtypes (85.7%) and NPV was higher in HER2+ and triple-negative tumors (83.3%).
- Single-center study with a modest sample size (n=68), limiting generalizability. - Only 68 of 109 screened patients were included, raising selection bias concerns. - Overall diagnostic accuracy was low, and the study was not powered to formally compare performance across molecular subtypes.
PET/MRI does not offer a clear advantage over axillary ultrasound for post-PST nodal staging in unselected node-positive breast cancer patients. Subtype-tailored imaging strategies — particularly leveraging PET/MRI's higher NPV in HER2+ and triple-negative disease — may be worth exploring in future trials before changing surgical decision-making.
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