QDB method shows higher consistency than IHC for HER2 assessment in invasive breast cancer

This observational cohort study evaluated a Quantitative Dot Blot (QDB) method against standard immunohistochemistry (IHC) for HER2 assessment in patients with invasive breast cancer. The population included patients with HER2 IHC 0 and 1+ from invasive breast cancer, with a training cohort of n=106 and a validation cohort of n=119.

The primary outcome was the consistency of HER2 assessment. For inter-rater Intraclass Correlation Coefficient (ICC), QDB was more consistent than IHC, with an effect size of 0.877 vs. 0.513. The 95% confidence intervals were 0.840-0.908 for QDB and 0.433-0.601 for IHC. For Area Under the Curve (AUC), ROC analysis benchmarked with unanimous agreement of 18 pathologists yielded an effect size of 0.9477; the p-value was not reported.

Safety and tolerability were not reported, including adverse events, serious adverse events, and discontinuations. Key limitations include the observational design, which cannot establish causality, and the lack of reported follow-up duration or funding details.

The practice relevance is guiding trastuzumab deruxtecan therapy, but these findings are preliminary and require further validation in prospective studies.