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The POWER trial: A randomised, two-armed open label phase 3 clinical trial on personalised dose optimisation with adjuvant tamoxifen therapy after breast cancer to investigate the impact on discontinuation and efficacy compared to standard of care
EU CTIS ID: 2025-522240-40-00
What this study is testing
The primary objective of this trial is to investigate the effect of personalised dosing of tamoxifen (10 mg, 20 mg or 40 mg per day) on tamoxifen discontinuation compared to the standard regimen (20 mg per day).
- Therapeutic confirmatory (Phase III)
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 primary breast cancer, recommended for adjuvant tamoxifen treatment with or without concomitant goserelin
- Women aged >18 years to ≤ 75 years
- ECOG WHO PS 0 – 2
- Participants must use non-hormonal contraception during the trial. A pregnancy test is recommended for women of child-bearing potential who are sexually active and not using reliable contraceptive methods before inclusion
- Able and willing to undergo blood sampling according to study protocol
- Able and willing to give their written consent to participate in the trial
You likely can't join if
- Previous or ongoing use of tamoxifen or endoxifen. Could be allowed after discussion with Sponsor E.g. treatment with tamoxifen for previous primary breast cancer
- Uncontrolled intercurrent physical or psychiatric illness, or social situations that would limit compliance with protocol requirements
- Prior invasive malignancy during the last five years. Prior or current in situ cancers are allowed
- Participation in another clinical drug trial
- Inability to understand the study related information
- Ongoing treatment with adjuvant CDK4/6 inhibitors or capecitabine or trastuzumab emtansin. Previous treatment with CDK4/6 inhibitors, capatecitabine or trastuzumab emtansin is allowed.
See the full eligibility criteria
- Patients with primary breast cancer, recommended for adjuvant tamoxifen treatment with or without concomitant goserelin
- Women aged >18 years to ≤ 75 years
- ECOG WHO PS 0 – 2
- Participants must use non-hormonal contraception during the trial. A pregnancy test is recommended for women of child-bearing potential who are sexually active and not using reliable contraceptive methods before inclusion
- Able and willing to undergo blood sampling according to study protocol
- Able and willing to give their written consent to participate in the trial
- More than 2.5 years left of planned tamoxifen treatment if switching from aromatase inhibitors.
- Previous or ongoing use of tamoxifen or endoxifen. Could be allowed after discussion with Sponsor E.g. treatment with tamoxifen for previous primary breast cancer
- Uncontrolled intercurrent physical or psychiatric illness, or social situations that would limit compliance with protocol requirements
- Prior invasive malignancy during the last five years. Prior or current in situ cancers are allowed
- Participation in another clinical drug trial
- Inability to understand the study related information
- Ongoing treatment with adjuvant CDK4/6 inhibitors or capecitabine or trastuzumab emtansin. Previous treatment with CDK4/6 inhibitors, capatecitabine or trastuzumab emtansin is allowed.
- Previous medical history of: Deep venous thrombosis or pulmonary embolism if not on life-long anticoagulant treatment with DOAC. A history of previous PICC-line or subcutaneous venous port associated thrombosis or superficial thrombophlebitis is allowed. Bleeding disorder or coagulopathy. Macular disorders, retinal disorder, severe cataract or glaucoma.
- Current use of warfarin. Antiaggregants’ and direct oral anticoagulants are allowed
- Not willing to abstain from strong and moderate CYP2D6 inhibitors or CYP3A4 inducers during the tamoxifen treatment
- Strong and moderate inhibitors of CYP2D6 not allowed in the trial: Bupropion (Zyban), Duloxetin (Cymbalta), Fluoxetin (Fontex), Levemopromazin (Nozinan), Mirabegron (Betmiga), Paroxetin (Seroxat), Terbinafin (Lamisil) for systemic use.
- CYP3A4 inducers not allowed in the trial (D-interactions in “Janusmedicin” janusmed.se): Efavirenz, Fenobarbital, Fenytoin, Johannesört, Karbamazepin, Primidon, Rifampicin, rifamycin.
- Current pregnancy, breastfeeding, or already at start of tamoxifen planning to become pregnant within the next two years
- Use of systemic menopausal hormonal therapy (MHT) and all types of systemic hormonal contraception. Local treatment is acceptable
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 female, 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.