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Trastuzumab Deruxtecan for HER2-Low Breast Cancer: Antibody-Drug Conjugate Expanding HER2-Targeted Therapy

Novel ADC redefining HER2 expression categories enabling targeted therapy benefit in previously HER2-negative breast cancer

Written by: Saygı Hospital Health Guide Editorial Board
Last updated:

This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

References (5)

This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Onkoloji department. Book Appointment →

What is Trastuzumab Deruxtecan for HER2-Low Breast Cancer: Antibody-Drug Conjugate Expanding HER2-Targeted Therapy?

Trastuzumab deruxtecan (T-DXd) is antibody-drug conjugate combining trastuzumab with deruxtecan topoisomerase I inhibitor through cleavable linker.

Drug-to-antibody ratio of approximately 8 enables enhanced tumor cell killing with bystander effect on neighboring HER2-low cells.

HER2-low breast cancer encompasses IHC 1+ tumors and IHC 2+ tumors with negative in situ hybridization representing 45-55% of breast cancers.

DESTINY-Breast04 trial demonstrated overall survival benefit versus chemotherapy of physician's choice in pretreated HER2-low metastatic breast cancer.

Approval extends HER2-targeted therapy benefit to substantial population previously classified as HER2-negative without targeted options.

Symptoms

Interstitial lung disease and pneumonitis represent serious treatment-related adverse events requiring vigilant monitoring and prompt intervention.
Nausea and vomiting are common requiring effective antiemetic prophylaxis with NK1 antagonists, 5HT3 antagonists and dexamethasone.
Fatigue and alopecia affect quality of life requiring supportive care and patient counseling.
Cytopenias including neutropenia, anemia and thrombocytopenia require complete blood count monitoring and dose modification.
Cardiac dysfunction with left ventricular ejection fraction decline parallels other HER2-targeted agents requiring echocardiogram surveillance.

Risk Factors

Pre-existing pulmonary disease, prior lung radiation or smoking history may increase interstitial lung disease risk during treatment.
Concurrent or prior anthracycline exposure increases cardiotoxicity risk requiring careful cardiac function monitoring.
Strong CYP3A4 inhibitors require dose modification given drug metabolism and potential interaction effects.
Pregnancy and breastfeeding contraindications given fetal risks from cytotoxic payload.
Hepatic impairment requires dose adjustments per established criteria and careful monitoring.

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • HER2-low metastatic breast cancer after at least one prior chemotherapy regimen warrants T-DXd consideration.
  • New respiratory symptoms during treatment including dyspnea, cough or chest discomfort require urgent evaluation excluding pneumonitis.
  • Imaging surveillance every 6-9 weeks for the first 6 months identifies early pulmonary changes warranting intervention.
  • Severe nausea, vomiting or weight loss requires antiemetic optimization and supportive care.
  • Cardiac symptoms or decline in ejection fraction warrant cardiology consultation and treatment modification consideration.

Treatment Methods

01
Trastuzumab deruxtecan 5.4 mg/kg IV every 3 weeks until progression or unacceptable toxicity represents standard regimen.
02
Antiemetic prophylaxis with three-drug combination including NK1 antagonist, 5HT3 antagonist and corticosteroid.
03
Pneumonitis monitoring with baseline and serial CT imaging plus high-resolution CT at any new respiratory symptom.
04
Pneumonitis management with treatment hold, corticosteroids and pulmonology consultation per severity grading.
05
Comprehensive supportive care, cardiac monitoring, hematology surveillance and patient education supports safe administration of this transformative agent expanding HER2-targeted therapy benefit to previously underserved patient population.

Which Department to Visit?

You can visit our Onkoloji department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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