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Observational study of trastuzumab deruxtecan for patients with HER2-low breast cancer

REal-world Study of Trastuzumab deruXtecan in Patients With unresectabLe or Metastatic Breast Cancer Expressing HER2-lOw From BulgaRia and SlovEnia (EXPLORE)

Observational AstraZeneca · NCT06727227

This study is looking at how well trastuzumab deruxtecan works for people with HER2-low breast cancer that can't be removed by surgery or has spread, focusing on real-world experiences in Bulgaria and Slovenia.

Quick facts

Study typeObservational
Enrollment135 (estimated)
Ages18 Years and up
SexAll
SponsorAstraZeneca Industry-sponsored
Drugs / interventionschemotherapy, trastuzumab
Locations14 sites (Panagyurishte, Pazardzhik and 13 other locations)
Trial IDNCT06727227 on ClinicalTrials.gov

What this trial studies

This observational study aims to gather real-world data on the use of trastuzumab deruxtecan in patients with unresectable or metastatic HER2-low breast cancer in Bulgaria and Slovenia. It will assess various outcomes, including time to next treatment and treatment discontinuation, while also documenting patient demographics and treatment patterns prior to T-DXd therapy. The study seeks to fill the gap in real-world evidence for this treatment approach, particularly in the Balkan region, following its recent approval for HER2-low breast cancer. No formal hypothesis is set, and the study will explore multiple endpoints related to treatment effectiveness and patient management.

Who should consider this trial

Good fit: Ideal candidates include adults aged 18 and older with confirmed unresectable or metastatic HER2-low breast cancer who have received prior chemotherapy.

Not a fit: Patients who are pregnant, breastfeeding, or have a history of other primary malignancies within the last two years may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could provide valuable insights into the effectiveness of trastuzumab deruxtecan for patients with HER2-low breast cancer, potentially improving treatment strategies.

How similar studies have performed: While there is limited real-world evidence for trastuzumab deruxtecan in HER2-low breast cancer, the recent DB-04 trial has shown significant survival benefits, indicating potential success for this approach.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* Adult patient (age ≥18 years) with histological or cytological confirmed diagnosis of unresectable or mBC.
* Documented HER2-low status (IHC1+, IHC2+/ISH-) in patients who have received prior chemotherapy in the metastatic setting or documented HER2-low status (IHC 1+, IHC 2+/ISH-) in patients who have developed disease recurrence during or within 6 months of completing adjuvant chemotherapy.
* Recent prior decision to initiate therapy of T-DXd per SmPC (up to 30 days). Documentation confirming this decision will be required and collected.
* Able and willing to provide informed consent.

Exclusion Criteria:

* Pregnancy or breastfeeding.
* History of other primary malignancies in 2 years prior to unresectable or mBC diagnosis.
* Patients who at time of data collection for this study are participating in or have participated in an interventional study that remains blinded.
* HER2-low status patients who have previously documented HER2+ status in the same tumor.

Where this trial is running

Panagyurishte, Pazardzhik and 13 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Breast Cancer
Last reviewed 2026-06-10 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.