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ENDO-67 project: Investigating ENDOcrine therapy-related questions using Ki67 changes in the window-of-opportunity before breast surgery
EU CTIS ID: 2025-521385-10-00
What this study is testing
1. Can steady-state levels of endoxifen be achieved within three (rather than twelve) weeks using the PK model-derived tamoxifen loading schedule? 2. Can ER-pathway inactivity, measured by percentage Ki67 before and after treatment in ER positive tumours, reliable predict tamoxifen insensitivity? 3. What is de correlation between intratumoral endoxifen levels and Ki67 response?
- Therapeutic use (Phase IV)
A plain-language read of the study's public EU CTIS listing. The study team confirms the details.
Who can take part
You may be able to join if
- Patients with treatment naïve, ≥cT1c ER+, Her2- primary breast cancer (tumor still in situ) with a Ki-67 ≥10%
- Age older than 18 year
- An indication for postoperatively endocrine treatment
- WHO performance status 0-2
- The primary breast tumor should be amendable for multiple biopsies
- Specific for tamoxifen: Indication for adjuvant tamoxifen treatment
You likely can't join if
- Women who are pregnant or breast feeding
- Patients in whom neoadjuvant chemotherapy is indicated and delay is not desirable
- Patients with known alcoholism, drug addiction and/or psychiatric of physiological condition which in the opinion of the investigator would impair treatment compliance
- Evidence of any other disease, neurological or metabolic dysfunction, physical examination finding or laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of endocrine treatment or puts the patient at high risk for treatment related complications.
- Specific for tamoxifen: Endometrial cancer (diagnosis < 3 years ago)
- Specific for tamoxifen: • Use of strong CYP2D6-inhibitors without the possibility to stop this medication
See the full eligibility criteria
- Patients with treatment naïve, ≥cT1c ER+, Her2- primary breast cancer (tumor still in situ) with a Ki-67 ≥10%
- Age older than 18 year
- An indication for postoperatively endocrine treatment
- WHO performance status 0-2
- The primary breast tumor should be amendable for multiple biopsies
- Specific for tamoxifen: Indication for adjuvant tamoxifen treatment
- Women who are pregnant or breast feeding
- Patients in whom neoadjuvant chemotherapy is indicated and delay is not desirable
- Patients with known alcoholism, drug addiction and/or psychiatric of physiological condition which in the opinion of the investigator would impair treatment compliance
- Evidence of any other disease, neurological or metabolic dysfunction, physical examination finding or laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of endocrine treatment or puts the patient at high risk for treatment related complications.
- Specific for tamoxifen: Endometrial cancer (diagnosis < 3 years ago)
- Specific for tamoxifen: • Use of strong CYP2D6-inhibitors without the possibility to stop this medication
- Specific for tamoxifen: • Concomitant use of over-the-counter-drugs, herbal or homeopathic remedies which (may) interfere with tamoxifen and not willing to stop such as (but not limited to ) St. John’s Wort, curcuma/piperine
- Specific for tamoxifen: Known poor metabolizer of CYP2D6
The study team makes the final eligibility decision.
Questions & answers
Do participants get paid in this trial?
This listing doesn't specify compensation. Many trials still reimburse travel or offer a stipend, so it's worth asking the study team when you connect.
Is it free to join, and do I need insurance?
Searching and applying through BridgeMD is free. In clinical trials the study-related treatment and visits are generally provided at no cost to you. You usually don't need insurance to take part - confirm specifics with the study team.
How long does this study last?
The listing doesn't state an exact length. The study team walks you through the schedule and number of visits before you decide to enroll.
Who can join this trial?
This study is enrolling all sexes, 18-64 years, 65+ years. The study team makes the final eligibility decision.
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BridgeMD is an information and trial-matching tool - not medical advice, and not the study sponsor. Details come from EU CTIS; the study team decides eligibility.