Integrating Practice with Precision: A Quantitative HER2 Protein Assay Developed for Clinical Application in Trastuzumab Deruxtecan Treatment Guidance - Report - MDSpire

Integrating Practice with Precision: A Quantitative HER2 Protein Assay Developed for Clinical Application in Trastuzumab Deruxtecan Treatment Guidance

  • By

  • Junmei Hao

  • Xiaochun Fei

  • Fangfang Zou

  • Qian Hu

  • Linlin Du

  • Liya Yu

  • Xuanye Bai

  • Shasha Bi

  • Qinghua Cao

  • Weishan Chen

  • Qun Dai

  • Tingting Guo

  • Hai Huang

  • Wenwei Jiang

  • Baohua Li

  • Lixia Li

  • Jingjing Liu

  • Tong Liu

  • Xiaoqin Liu

  • Jiahong Lyu

  • Yue Pan

  • Xiaoqing Shao

  • Fangrong Tang

  • Tingting Wang

  • Cuiping Zhang

  • Yongcun Zhu

  • Job Tien Chiang Liu

  • Nicole Salazar

  • Shukun Zhang

  • Jiandi Zhang

  • Xiaosong Chen

  • Chaofu Wang

  • April 27, 2026

  • 0 min

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Clinical Report: Quantitative HER2 Assay for Trastuzumab Deruxtecan Guidance

Overview

Expand on the implications of accurately distinguishing HER2-low from HER2-0 patients.

Background

The assessment of HER2 status is crucial for the effective treatment of breast cancer, particularly with the advent of therapies like Trastuzumab Deruxtecan (T-DXd). Traditional methods, such as immunohistochemistry (IHC), have shown limitations in accurately classifying HER2 levels, especially in low-expressing tumors. This study addresses the need for a more reliable quantitative assay to improve patient stratification and treatment outcomes.

Data Highlights

MethodInter-rater ICCAUCConcordance
QDB0.8770.947790.9%
IHC0.513N/A87.3%

Key Findings

  • The QDB assay demonstrated a higher inter-rater ICC of 0.877 compared to IHC's 0.513.
  • ROC analysis yielded an AUC of 0.9477 for the QDB method.
  • A cutoff of 0.2746 nmole/g was established to differentiate HER2 levels.
  • Approximately 15% of specimens classified as IHC 0 were identified as 1+ by QDB.
  • The QDB assay achieved overall concordance rates of 90.9% and 92.0% in training and validation cohorts, respectively.

Clinical Implications

The QDB assay offers a more reliable method for HER2 assessment, potentially improving treatment decisions for patients eligible for T-DXd. Clinicians should consider integrating this quantitative approach into routine practice to enhance patient stratification and therapeutic outcomes.

Conclusion

The QDB HER2 assay presents a promising alternative to traditional IHC methods, addressing significant gaps in the accurate classification of HER2 status in breast cancer. Its implementation could lead to improved treatment guidance for patients receiving Trastuzumab Deruxtecan.

References

  1. The ASCO Post, 2011 -- Optimizing HER2-directed Therapy in the Clinic
  2. The ASCO Post, 2015 -- Understanding the Role of Immune Function in the Treatment of HER2-Positive Breast Cancer
  3. The ASCO Post, 2023 -- ASCO-CAP Guideline Update Confirms Previous Recommendations for HER2 Testing in Breast Cancer
  4. The ASCO Post, 2022 -- ASCO Treatment Guidelines for HER2-Negative Metastatic Breast Cancer Updated to Reflect New Trastuzumab Deruxtecan Data
  5. HER2 Testing in Breast Cancer - College of American Pathologists
  6. Trastuzumab Deruxtecan in Low or Ultralow HER2 Metastatic Breast Cancer - PubMed
  7. HER2 Testing in Breast Cancer -… | College of American Pathologists
  8. Trastuzumab Deruxtecan in Low or Ultralow HER2 Metastatic Breast Cancer - PubMed
  9. Full article: Efficacy and safety of trastuzumab deruxtecan in HER2-high and HER2-low breast cancer: a systematic review and meta-analysis of randomized controlled trials

Original Source(s)

Integrating Practice with Precision: A Quantitative HER2 Protein Assay Developed for Clinical Application in Trastuzumab Deruxtecan Treatment Guidance

  • by Junmei Hao, Xiaochun Fei, Fangfang Zou, Qian Hu, Linlin Du, Liya Yu, Xuanye Bai, Shasha Bi, Qinghua Cao, Weishan Chen, Qun Dai, Tingting Guo, Hai Huang, Wenwei Jiang, Baohua Li, Lixia Li, Jingjing Liu, Tong Liu, Xiaoqin Liu, Jiahong Lyu, Yue Pan, Xiaoqing Shao, Fangrong Tang, Tingting Wang, Cuiping Zhang, Yongcun Zhu, Job Tien Chiang Liu, Nicole Salazar, Shukun Zhang, Jiandi Zhang, Xiaosong Chen, Chaofu Wang

  • April 27, 2026

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