Breast CancerEXPLORENCT06727227
Real-world Study of Trastuzumab Deruxtecan in Patients With Unresectable or Metastatic HER2-low Breast Cancer
An observational study of Breast Cancer, run by AstraZeneca at 14 sites in 2 countries.
Trial summary
A longitudinal, non-interventional study with trastuzumab deruxtecan for patients with HER2-low expressing unresectable or metastatic breast cancer in Bulgaria and Slovenia Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Breast Cancer
- What is being tested?
- trastuzumab deruxtecan
- How many people
- 138 participants
- Where
- 14 sitesin 2 countries
- Study dates
- 29 Jan 2025to 31 Oct 2027
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: Study Population: Criteria: Age: Adult patients (≥18 years). Diagnosis: Confirmed diagnosis of unresectable or metastatic breast cancer (mBC). HER2 Status: Documented HER2-low status. Treatment Decision: Patients for whom the decision to initiate trastuzumab deruxtecan (T-DXd) treatment has been made independently and prior to enrolment in the study. Enrollment: Timing: Patients must be enrolled within 30 days before the administration of the first T-DXd infusion. Consent: Patients must provide written informed consent for data collection.
Who may be able to join
- 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.
Who cannot join
- 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.
Trial locations and contacts
14 sites in 2 countries. Contact the study team or a site near you to ask about taking part.
AstraZeneca Clinical Study Information Center, Study Information Center contact
14 sites in 2 countries
Bulgaria12 sites, 6 recruiting
- Recruiting
Research Site
Burgas, 8000
+35956 531068, odisp@abv.bg
Ivan Bivolarski, Dr.
- Not yet recruiting
Research Site
Panagyurishte, Pazardzhik, 4500
+359884 296 946, uni@unihospitalbg.bg
Rossitza Krasteva, Dr.
- Not yet recruiting
Research Site
Plovdiv, 4004
+35932277240, kocplovdiv@onkoplov.com
Ivan Tonev, Dr.
- Active, not recruiting
Research Site
Sofia, 1303
- Active, not recruiting
Research Site
Sofia, 1330
- Not yet recruiting
Research Site
Sofia, 1407
+35924034000
Jeliazko Arabadjiev
- Active, not recruiting
Research Site
Sofia, 1431
- Active, not recruiting
Research Site
Sofia, 1527
- Not yet recruiting
Research Site
Sofia, 1618
+3592 818 46 00, svsofia@mbal-sofia.com
Marchela Koleva, Dr.
- Active, not recruiting
Research Site
Sofia, 1756
- Not yet recruiting
Research Site
Stara Zagora, 6003
+35942614196, oncosz@abv.bg
Bozhidara Kostova, Dr.
- Active, not recruiting
Research Site
Varna, 9003
Slovenia2 sites, 2 recruiting
- Recruiting
Research Site
Ljubljana, 1000
info@onko-i.si
Principal Investigator
- Recruiting
Research Site
Maribor, 2000
pisarna@ukc-mb.si
Principal Investigator
About this study
Official title: REal-world Study of Trastuzumab deruXtecan in Patients With unresectabLe or Metastatic Breast Cancer Expressing HER2-lOw From BulgaRia and SlovEnia (EXPLORE)
A longitudinal, non-interventional study with trastuzumab deruxtecan for patients with HER2-low expressing unresectable or metastatic breast cancer in Bulgaria and Slovenia
Read the detailed description
EXPLORE Non-Interventional Study for HER2-low Breast Cancer Treatment with T-DXd
Background:
HER2 is a prognostic marker in various cancers, including breast cancer (BC). Traditionally categorized as HER2-positive or HER2-negative, recent advancements with anti-HER2 ADCs, like trastuzumab deruxtecan (T-DXd), have shown benefits for HER2-low status BC. The DB-04 trial demonstrated significant survival benefits with T-DXd, leading to its EMA approval for HER2-low BC in January 2023.
Study Rationale:
Limited real-world evidence exists for T-DXd in HER2-low BC, particularly in the Balkans. The EXPLORE study aims to fill this gap by collecting real-world data in Bulgaria and Slovenia.
Objectives:
Primary Objective:
Describe real-world Time to Next Treatment (rwTTNT1) of T-DXd in HER2-low unresectable or metastatic BC (mBC).
Secondary Objectives:
Describe pre-T-DXd treatment patterns at baseline. Describe patient demographics and clinical characteristics at baseline. Describe rwTTNT1 by prior therapy lines in the metastatic setting and by hormone receptor (HR) status.
Evaluate real-world Time to Treatment Discontinuation (rwTTD1).
Exploratory Objectives:
Evaluate real-world progression-free survival (rwPFS1). Characterize subsequent treatments and post-progression endpoints (rwTTNT2, rwTTD2, rwPFS2).
Describe biopsy patterns. Evaluate reasons for discontinuation (rwTTNT1 and rwTTNT2). Describe T-DXd treatment changes over time. No formal hypothesis is set.
Methods:
Study Design:
Observational, longitudinal, non-interventional study in Bulgaria and Slovenia. Patients with unresectable or mBC starting T-DXd within 30 days of enrolment. Data from hospital charts at routine visits.
Population:
Adults (≥18 years) with HER2-low mBC, initiating T-DXd independent of the study.
Exposure:
T-DXd treatment details (dose, duration) and other therapies recorded. Recommended T-DXd dose: 5.4 mg/kg IV every 3 weeks.
Outcomes:
Primary: Time from T-DXd initiation to subsequent therapy or death. Exploratory: Various survival measures, biopsy patterns, reasons for discontinuation, and treatment changes.
Sample Size:
Approximately 135 patients (100 in Bulgaria, 35 in Slovenia).
Statistical Analysis:
Descriptive analyses for cohort characteristics. Kaplan-Meier method for time-to-event endpoints. Subgroup analyses by prior therapy lines and HR status.
Data Collection:
Data from paper or electronic health records. Single anonymized dataset via electronic case report forms (CRFs).
- Conditions
- Breast Cancer
- Being tested
- trastuzumab deruxtecan
- Medical subject headings
- Breast Neoplasms
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
trastuzumab deruxtecanDrug
T-DXd
What is being measured
The primary outcome is the main question the study is designed to answer.
Real-world Time to Next Treatment (rwTTNT1, median, 95% CI, measured in months)
The duration from initiation of trastuzumab deruxtecan (T-DXd) treatment to the start of the subsequent therapy or death from any cause, whichever occurs first, assessed up to 19 months.
Measured: Baseline up to 19 months
Secondary outcomes (15)
Describe type and proportion of previous treatments for unresectable or mBC and comorbidities
Prior treatments: surgery, chemotherapy, radiotherapy, therapies in neoadjuvant/adjuvant/advanced setting; treatment line (special focus should be given on endocrine and chemotherapy recycling in the metastatic setting). The timeline for these treatments will include all therapies administered from the time of breast cancer diagnosis.
Measured: Baseline
Duration of previous treatments and number of treatment lines
Start and stop date, if available
Measured: Baseline
Response to previous treatments
To describe patients' response to previous treatment, as applicable: clinical response (partial response/complete response/stable disease/disease progression; if progression: date and site of progression)
Measured: Baseline
Mean (SD) age at diagnosis
Describe the patients' mean (SD) age at diagnosis
Measured: Baseline
Mean (SD) age at T-DXd start
To describe patients' mean (SD) age at T-DXd start
Measured: Baseline
Proportion of males and females
To describe the proportion of males and females
Measured: Baseline
Proportion of patients with HR+ vs HR- tumors
Describe the proportion of patients with HR+ vs HR- tumors
Measured: Baseline
Distribution by smoking status
Describe the patients' smoking status. Includes electronic cigarettes/vapes
Measured: Baseline
Type and proportion of comorbidities
Comorbidities (including cardiovascular diseases, pulmonary disorders, hepatic disorders, renal disorders, blood and lymphatic system disorders, metabolism and nutrition disorders, gastrointestinal disorders, hepatobiliary disorders, central nervous system [CNS] disorders, eye disorders, skin disorders and musculoskeletal and connective tissue disorders, infections and infestations and other relevant
Measured: Baseline
Distribution by ECOG status
Describe patients' ECOG PS at index date
Measured: Baseline
mean (SD) duration of disease (at index), measured in months or years
Describe patients' mean duration of disease through date of initial diagnosis and date of diagnosis of unresectable or metastatic breast cancer, as applicable
Measured: Baseline
HER2-low status and type and proportion of metastatic sites
Describe patients' HER2-low status and type and proportion of metastatic sites through most recent HER2-low status, new metastatic sites since the time of mBC diagnosis, disease burden (all disease sites, including the presence/absence of brain metastases [stable/active]
Measured: Baseline
rwTTNT1 by Number of Prior of Therapy Lines for Metastatic Disease (median, 95% CI, measured in months, 1 vs 2 vs 3+ Lines)
Describe rwTTNT1 stratified by the number of prior therapy lines in the metastatic setting.
Measured: Baseline up to 19 months
rwTTNT1 by HR-status (median, 95% CI, measured in months, HR+ vs HR-)
Describe rwTTNT1 stratified by hormone receptor (HR) status.
Measured: Baseline up to 19 months
Real-world Time to Treatment Discontinuation (rwTTD1, median, 95% CI, measured in months)
Evaluate the duration from the start of T-DXd treatment until its discontinuation or death, whichever occurs first.
Measured: Baseline up to 19 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Dec 2024
- Study start29 Jan 2025
- Primary completion31 Oct 2027 (estimated)
- Study completion31 Oct 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Breast CancerStudies of the same condition, open and under way.
- More trials run by AstraZenecaThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Other
- Enrolment
- 138 participants (estimated)
Sponsor and investigators
- Lead sponsor
- AstraZeneca
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06727227
- Sponsor's protocol ID
- D9673R00055
- Acronym
- EXPLORE
- Status last verified
- Sep 2026
- First submitted
- 20 Nov 2024
- Last updated
- 14 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal Vivli.org. All requests will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure
Study at a glance
From the registry record, last updated by the sponsor on 14 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- REal-world Study of Trastuzumab deruXtecan in Patients With unresectabLe or Metastatic Breast Cancer Expressing HER2-lOw From BulgaRia and SlovEnia (EXPLORE)
- ClinicalTrials.gov ID
- NCT06727227
- Acronym / sponsor ID
- EXPLORE / D9673R00055
- Conditions
- Breast Cancer
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 138 participants (estimated)
- Lead sponsor
- AstraZenecaIndustry (pharma, biotech, devices)
- Study start
- 29 Jan 2025 (actual)
- Primary completion
- 31 Oct 2027 (estimated)
- Study completion
- 31 Oct 2027 (estimated)
- First posted
- 10 Dec 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
A longitudinal, non-interventional study with trastuzumab deruxtecan for patients with HER2-low expressing unresectable or metastatic breast cancer in Bulgaria and Slovenia
Detailed description
EXPLORE Non-Interventional Study for HER2-low Breast Cancer Treatment with T-DXd
Background:
HER2 is a prognostic marker in various cancers, including breast cancer (BC). Traditionally categorized as HER2-positive or HER2-negative, recent advancements with anti-HER2 ADCs, like trastuzumab deruxtecan (T-DXd), have shown benefits for HER2-low status BC. The DB-04 trial demonstrated significant survival benefits with T-DXd, leading to its EMA approval for HER2-low BC in January 2023.
Study Rationale:
Limited real-world evidence exists for T-DXd in HER2-low BC, particularly in the Balkans. The EXPLORE study aims to fill this gap by collecting real-world data in Bulgaria and Slovenia.
Objectives:
Primary Objective:
Describe real-world Time to Next Treatment (rwTTNT1) of T-DXd in HER2-low unresectable or metastatic BC (mBC).
Secondary Objectives:
Describe pre-T-DXd treatment patterns at baseline. Describe patient demographics and clinical characteristics at baseline. Describe rwTTNT1 by prior therapy lines in the metastatic setting and by hormone receptor (HR) status.
Evaluate real-world Time to Treatment Discontinuation (rwTTD1).
Exploratory Objectives:
Evaluate real-world progression-free survival (rwPFS1). Characterize subsequent treatments and post-progression endpoints (rwTTNT2, rwTTD2, rwPFS2).
Describe biopsy patterns. Evaluate reasons for discontinuation (rwTTNT1 and rwTTNT2). Describe T-DXd treatment changes over time. No formal hypothesis is set.
Methods:
Study Design:
Observational, longitudinal, non-interventional study in Bulgaria and Slovenia. Patients with unresectable or mBC starting T-DXd within 30 days of enrolment. Data from hospital charts at routine visits.
Population:
Adults (≥18 years) with HER2-low mBC, initiating T-DXd independent of the study.
Exposure:
T-DXd treatment details (dose, duration) and other therapies recorded. Recommended T-DXd dose: 5.4 mg/kg IV every 3 weeks.
Outcomes:
Primary: Time from T-DXd initiation to subsequent therapy or death. Exploratory: Various survival measures, biopsy patterns, reasons for discontinuation, and treatment changes.
Sample Size:
Approximately 135 patients (100 in Bulgaria, 35 in Slovenia).
Statistical Analysis:
Descriptive analyses for cohort characteristics. Kaplan-Meier method for time-to-event endpoints. Subgroup analyses by prior therapy lines and HR status.
Data Collection:
Data from paper or electronic health records. Single anonymized dataset via electronic case report forms (CRFs).
Study design
- Observational model
- Cohort
- Time perspective
- Other
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- Study Population: Criteria: Age: Adult patients (≥18 years). Diagnosis: Confirmed diagnosis of unresectable or metastatic breast cancer (mBC). HER2 Status: Documented HER2-low status. Treatment Decision: Patients for whom the decision to initiate trastuzumab deruxtecan (T-DXd) treatment has been made independently and prior to enrolment in the study. Enrollment: Timing: Patients must be enrolled within 30 days before the administration of the first T-DXd infusion. Consent: Patients must provide written informed consent for data collection.
Key inclusion criteria (4 listed)
- 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.
Key exclusion criteria (4 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| trastuzumab deruxtecanT-DXd | Drug | – |
Primary outcome
Real-world Time to Next Treatment (rwTTNT1, median, 95% CI, measured in months)
Time frame: Baseline up to 19 months
The duration from initiation of trastuzumab deruxtecan (T-DXd) treatment to the start of the subsequent therapy or death from any cause, whichever occurs first, assessed up to 19 months.
15 secondary outcomes
Describe type and proportion of previous treatments for unresectable or mBC and comorbidities
Time frame: Baseline
Duration of previous treatments and number of treatment lines
Time frame: Baseline
Response to previous treatments
Time frame: Baseline
Mean (SD) age at diagnosis
Time frame: Baseline
Mean (SD) age at T-DXd start
Time frame: Baseline
Proportion of males and females
Time frame: Baseline
Proportion of patients with HR+ vs HR- tumors
Time frame: Baseline
Distribution by smoking status
Time frame: Baseline
Type and proportion of comorbidities
Time frame: Baseline
Distribution by ECOG status
Time frame: Baseline
mean (SD) duration of disease (at index), measured in months or years
Time frame: Baseline
HER2-low status and type and proportion of metastatic sites
Time frame: Baseline
rwTTNT1 by Number of Prior of Therapy Lines for Metastatic Disease (median, 95% CI, measured in months, 1 vs 2 vs 3+ Lines)
Time frame: Baseline up to 19 months
rwTTNT1 by HR-status (median, 95% CI, measured in months, HR+ vs HR-)
Time frame: Baseline up to 19 months
Real-world Time to Treatment Discontinuation (rwTTD1, median, 95% CI, measured in months)
Time frame: Baseline up to 19 months
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 14 Sep 2026.
- Individual participant dataSharing planned: Yes. Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal Vivli.org. All requests will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
AstraZeneca Clinical Study Information Center, Study Information Center contact
14 sites in 2 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Breast Cancer, run by AstraZeneca at 14 sites in 2 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 14 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 14 sites in Bulgaria, Slovenia. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact AstraZeneca Clinical Study Information Center, Study Information Center (1-877-240-9479, information.center@astrazeneca.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Real-world Time to Next Treatment (rwTTNT1, median, 95% CI, measured in months) (time frame: Baseline up to 19 months). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 14 Sep 2026.