The POWER Trial: Personalised Dose Optimisation With Adjuvant Tamoxifen Therapy in Breast cancER
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: Individual dose of tamoxifen, Standard adjuvant therapy of tamoxifen.
- Who it may be relevant to
- Registry conditions: Breast Cancer, Adjuvant Drug Therapy. Basic parameters: from 18 years · Female.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Sweden
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
Unsure about the terms? Read our patient guide →
Official title
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
Overview
In Sweden, approximately 7000 women are diagnosed with hormone-sensitive breast cancer annually. According to international and national guidelines, most of these women are recommended anti-hormonal therapy for five to ten years to improve prognosis. Tamoxifen, one of the most widely used anti-hormonal agents globally, reduces the risk of recurrence by 40% and breast cancer mortality by 30%. Tamoxifen is a pro-drug that undergoes hepatic metabolism to form endoxifen and other active metabolites. Variability in metabolic capacity affects therapeutic efficacy: poor metabolisers produce insufficient endoxifen and other active metabolites, risking therapeutic failure, while ultrarapid metabolisers generate excessive amounts, leading to intolerable adverse effects. Today, 30-50% of patients discontinue treatment prematurely due to severe side effects, resulting in suboptimal outcomes. Currently, tamoxifen is uniformly prescribed at a daily dose of 20 mg, and so far, no clinical trials have tested whether individualised dosing could enhance adherence and improve survival outcomes. The primary objective is to evaluate whether individualised tamoxifen dosing reduces discontinuation rates and enhances patient outcomes in breast cancer treatment.
Interventions
- Drug Individual dose of tamoxifen
Each subject starts their treatment with the standard dose 20 mg tamoxifen daily by oral intake. During visits 2 (3 months), 3 (six months) and 4 (twelve months), the investigator will either let the patient remain on 20 mg tamoxifen or individualise the dose. The investigator may change the daily tamoxifen from 20 mg per day to: a halved dose to 10 mg, or a doubled dose to 40 mg. The recommendation for oral intake of tablet(s) tamoxifen for a daily dose of 10, 20 or 40 mg is accordingly: fo - Drug Standard adjuvant therapy of tamoxifen
The global standard dose for everyone is 20 mg orally once per day. Each subject undergoes treatment with the standard dose 20 mg daily by oral intake of one tablet, with no possibility of dose adjustment during the trial.
Primary outcome measures
- Discontinuation of tamoxifen. [Time frame: From enrollment to end of treatment at 60 months.]
Secondary outcome measures (11)
- Patient reported outcomes. [Time frame: From enrollment to end of treatment at 60 months.]
- Quality of life questionnaire [Time frame: From enrollment to end of treatment at 60 months.]
- Concentration of circulation plasma metabolites [Time frame: From 3 months after treatment start to end of treatment at 60 months]
- Invasive disease-free survival (iDSF) [Time frame: From enrollment to end of treatment at 60 months.]
- Distant relapse-free survival (DRFS) [Time frame: From enrollment to end of treatment at 60 months.]
- Breast cancer specific survival (BCSS) [Time frame: From enrollment to end of treatment at 60 months.]
- Overall survival (OS) [Time frame: From enrollment to end of treatment at 60 months.]
- Mammographic breast density [Time frame: From enrollment to end of treatment at 60 months.]
- Cost effectiveness Analysis (CEA) [Time frame: From enrollment to end of treatment at 60 months.]
- Cost-Benefit Analysis (CBA) [Time frame: From enrollment to end of treatment at 60 months.]
- Incremental cost-effectiveness ratio (ICER) [Time frame: From enrollment to end of treatment at 60 months.]
Eligibility criteria
Inclusion criteria
- Patients with primary breast cancer, recommended for adjuvant tamoxifen treatment with or without concomitant goserelin
- Premenopausal or perimenopausal, defined according to SOC for therapy decision
- Eastern Cooperative Oncology Group (ECOG) WHO Performance Scale 0 - 2
- Participants must use non-hormonal contraception during the trial.
Exclusion criteria
- Previous use of tamoxifen, endoxifen, or aromatase inhibitors.
- Previous medical history of:
Deep venous thrombosis or pulmonary embolism; bleeding disorder or coagulopathy; macular disorders, retinal disorders, severe cataract or glaucoma.
- Current use of warfarin.
- Not willing to abstain from strong and moderate CYP2D6 inhibitors or CYP3A4 inducers during the tamoxifen treatment
- 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).
- Prior invasive malignancy during the last five years. Prior or current in situ cancers are allowed.
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Allocation
- Randomized
- Model
- Parallel assignment
- Masking
- Open label
- Primary purpose
- Treatment
Study locations
Sweden · 4 centers
- S:a Älvsborgs Sjukhus — Borås
- Skaraborgs Sjukhus — Skövde
- Capio S:t Görans Sjukhus — Stockholm
- Södersjukhuset, Onkologiska kliniken — Stockholm
Identifiers
NCT: NCT07502820 · 2025-522240-40-00