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Can a drug holiday keep breast cancer at bay longer?

NCT ID NCT00553410

Disease control Sponsor: ETOP IBCSG Partners Foundation Source: ClinicalTrials.gov ↗

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed This study
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Sep 01, 2026 · Last updated Sep 02, 2026 · Updated 1 time

Summary

This phase III trial tests whether taking letrozole continuously for five years is better than taking it in cycles with breaks, for postmenopausal women who have already had 4 to 6 years of hormone therapy for early-stage, hormone-receptor-positive breast cancer. Letrozole works by lowering estrogen levels, which can fuel breast cancer growth. The study compares disease-free survival and overall survival between the two schedules, aiming to find the most effective way to prevent recurrence.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance
letrozole
What this could lead to
If continuous letrozole proves better, it could extend the time women with early breast cancer stay cancer-free after standard hormone therapy.
What could go wrong
The trial is large but results may not apply to all patients, and letrozole can cause side effects like joint pain and hot flashes.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 3

Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.

Participants

4,884 people

The number who actually took part.

Start date

Aug 2007

Finished

May 2019

Lead sponsor

A research network

The lead sponsor is a research network or cooperative group.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 to 120 years

Sex

Female participants only

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

DISEASE CHARACTERISTICS: * Confirmed diagnosis of prior operable, noninflammatory breast cancer meeting the following criteria: * Steroid hormone receptor-positive tumors (estrogen receptor and/or progesterone receptor), determined by immunohistochemistry, after primary surgery and before commencement of prior endocrine therapy * Prior local treatment including surgery with or without radiotherapy for primary breast cancer with no known clinical residual loco-regional disease * Following primary surgery, eligible patients must have had evidence of lymph node involvement either in the axillary or internal mammary nodes, but not supraclavicular nodes * Clinically disease-free * Must have completed 4-6 years of prior adjuvant selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs), or a sequential combination of both * When calculating 4-6 years, neoadjuvant endocrine therapy should not be included * No evidence of recurrent disease or distant metastatic disease * No prior bilateral breast cancer PATIENT CHARACTERISTICS: * Female * Must be postmenopausal by any of the following criteria: * Patients of any age who have had a bilateral oophorectomy (including radiation castration AND amenorrheic for \> 3 months) * Patients 56 years old or older with any evidence of ovarian function must have biochemical evidence of definite postmenopausal status (defined as estradiol, luteinizing hormone \[LH\], and follicle-stimulating hormone \[FSH\] in the postmenopausal range) * Patients 55 years old or younger must have biochemical evidence of definite postmenopausal status (defined as estradiol, LH, and FSH in the postmenopausal range) * Patients who have received prior luteinizing-hormone releasing-hormone (LHRH) analogues within the last year are eligible if they have definite evidence of postmenopausal status as defined above * Clinically adequate hepatic function * No bone fracture due to osteoporosis at any time during the 4-6 years of prior therapy * No prior or current malignancy except adequately treated basal cell or squamous cell carcinoma of the skin, in situ carcinoma of the cervix or bladder, or contra- or ipsilateral in situ breast carcinoma * No other nonmalignant systemic diseases (cardiovascular, renal, lung, etc.) that would prevent prolonged follow-up * No psychiatric, addictive, or any other disorder that compromises compliance with protocol requirements PRIOR CONCURRENT THERAPY: * See Disease Characteristics * More than 12 months since prior and no other concurrent endocrine SERM/AI therapy * Any type of prior adjuvant therapy allowed including, but not limited to, any of the following: * Neoadjuvant chemotherapy * Neoadjuvant endocrine therapy * Adjuvant chemotherapy * Trastuzumab (Herceptin®) * Ovarian ablation * Gonadotropin releasing hormone analogues * Lapatinib ditosylate * No concurrent hormone-replacement therapy, bisphosphonates (except for treatment of bone loss), or any other investigational agent

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Conditions

The condition(s) this trial relates to.

breast cancer breast neoplasm hormone receptor-positive breast cancer

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Breast cancer

Contacts and locations

Locations

  • A. Perrino Hospital

    Brindisi, 72100, Italy

  • AZ Damiaan

    Ostend, 8400, Belgium

  • AZ Groeninge - Oncologisch Centrum

    Kortrijk, 8500, Belgium

  • AZ Klina

    Brasschaat, 2930, Belgium

  • AZ Nikolaas - Sint-Niklaas

    Sint-Niklaas, 9100, Belgium

  • Aalen Breast Center

    Aalen, 73430, Germany

  • Aarhus Universitetshospital - Aarhus Sygehus

    Aarhus C, DK-8000, Denmark

  • Academisch Ziekenhuis der Vrije Universiteit Brussel

    Brussels, 1090, Belgium

  • Algemeen Ziekenhuis Sint-Maarten - Campus Rooiberg

    Duffel, 2570, Belgium

  • Allgemeinen Krankenhaus Celle Kinderklinik

    Celle, 29223, Germany

  • Allgemeines Krankenhaus - Universitatskliniken

    Vienna, A-1090, Austria

  • Allgemeines Krankenhaus Linz

    Linz, A-4021, Austria

  • AndreasKlinik Cham Zug

    Cham, CH-6330, Switzerland

  • Armidale Hospital

    Armidale, New South Wales, 2350, Australia

  • Asklepios Klinik Lich

    Lich, D-35423, Germany

  • Austin Health

    Heidelberg, Victoria, 3084, Australia

  • Azienda Istituti Ospitalieri

    Cremona, 26100, Italy

  • Azienda Sanitaria di Bolzano

    Bolzano, 39100, Italy

  • Bankstown - Lidcombe Hospital

    Bankstown, New South Wales, 2200, Australia

  • Borders General Hospital

    Melrose, England, TD6 9BS, United Kingdom

  • Bornholms Hospital

    Rønne, 3700, Denmark

  • Box Hill Hospital

    Box Hill, Victoria, 3128, Australia

  • Breast Center

    Gateshead, New South Wales, 2290, Australia

  • Breast Center

    Zurich, CH-8008, Switzerland

  • Brustzentrum Thurgau at Kantonsspital Frauenfeld

    Frauenfeld, 8501, Switzerland

  • CHU Liege - Domaine Universitaire du Sart Tilman

    Liège, B-4000, Belgium

  • Calvary Mater Newcastle

    Waratah, New South Wales, 2310, Australia

  • Centralsygehus Esbjerg

    Esbjerg, DK-6700, Denmark

  • Centre Hospitalier Hutois

    Huy, 4500, Belgium

  • Centre Hospitalier Peltzer-La Tourelle

    Verviers, B-4800, Belgium

  • Centre Hospitalier Regional de la Citadelle

    Liège, 4000, Belgium

  • Centre Hospitalier Universitaire Brugmann

    Brussels, B 1020, Belgium

  • Centre Hospitalier Universitaire Vaudois

    Lausanne, CH-1011, Switzerland

  • Centre Hospitalier de l'Ardenne

    Libramont, 6800, Belgium

  • Centro di Riferimento Oncologico - Aviano

    Aviano, 33081, Italy

  • Christchurch Hospital

    Christchurch, 1, New Zealand

  • City Hospital Triemli

    Zurich, CH-8063, Switzerland

  • Clinique Saint Vincent

    Rocourt, 4000, Belgium

  • Clinique Saint-Joseph

    Liège, B 4000, Belgium

  • Clinique Saint-Pierre

    Ottignies, B-1340, Belgium

  • Cliniques Universitaires Saint-Luc

    Brussels, 1200, Belgium

  • Cliniques du Sud Luxembourg

    Arlon, 6700, Belgium

  • Concord Repatriation General Hospital

    Concord, New South Wales, 2139, Australia

  • Copenhagen County Herlev University Hospital

    Copenhagen, DK-2730, Denmark

  • Dana-Farber/Harvard Cancer Center at Dana-Farber Cancer Institute

    Boston, Massachusetts, 02115, United States

  • Deaconess Hospital

    Schwäbisch Hall, D-74523, Germany

  • Dumfries & Galloway Royal Infirmary

    Dumfries, Scotland, DG1 4AP, United Kingdom

  • European Institute of Oncology

    Milan, 20141, Italy

  • Faulkner Hospital

    Boston, Massachusetts, 02130-3400, United States

  • Fondazione Salvatore Maugeri

    Pavia, I-27100, Italy

  • Frauenheilkunde u. Geburtshilfe

    Ilsede, 31241, Germany

  • Fundacion Arturo Lopez Perez

    Santiago, 29, Chile

  • Gemeinschaftspraxis Gynaekologie & Geburtshilfe

    Mannheim, D68161, Germany

  • Gynaekologisch-onkologische Praxis Hannover

    Hanover, D-30177, Germany

  • Hanusch-Krankenhaus

    Vienna, A-1140, Austria

  • Henriettenstiftung Krankenhaus

    Hanover, D-30171, Germany

  • Herning Central Hospital

    Herning, DK-7400, Denmark

  • Hillerod Hospital

    Hillerød, 3400, Denmark

  • Hopital Regional de Sion-Herens-Conthey

    Sion, CH -1951, Switzerland

  • Hopital de Jolimont

    Haine-Saint-Paul, 7100, Belgium

  • Hospital Carlos Van Buren

    Valparaíso, Chile

  • Hospital Clinico Regional de Valdivia at University Austral de Chile

    Valdivia, Chile

  • Hospital Clinico San Borja Arriaran

    Santiago, Chile

  • Hospital Clinico Universitario de Valencia

    Valencia, 46010, Spain

  • Hospital Ramon y Cajal

    Madrid, 28034, Spain

  • Hospital Sant Joan de Reus

    Reus, 43201, Spain

  • Hospital Santiago Oriente Dr. Luis Tisne Brousse

    Peñalolén, 2005, Chile

  • Hospital Son Llatzer

    Palma de Mallorca, 07198, Spain

  • Hospital Universitario 12 de Octubre

    Madrid, 28041, Spain

  • Hospital Universitario Virgen Macarena

    Seville, 41009, Spain

  • Hospital de Torrevieja

    Torrevieja, 03180, Spain

  • IRAM - Chile

    Santiago, Chile

  • Imelda vzw, Ziekenhuis

    Bonheiden, 2820, Belgium

  • Innsbruck Universitaetsklinik

    Innsbruck, A-6020, Austria

  • Inselspital Bern

    Bern, CH-3010, Switzerland

  • Institut Bergonie

    Bordeaux, 33076, France

  • Institut Jules Bordet

    Brussels, 1000, Belgium

  • Instituto Nacional Del Cancer

    Santiago, Chile

  • Instituto Nacional de Enfermedades Neoplasicas

    Lima, 34, Peru

  • Instituto Valenciano De Oncologia

    Valencia, 46009, Spain

  • Istituto Oncologico della Svizzera Italiana - Ospedale San Giovanni

    Bellinzona, CH-6500, Switzerland

  • Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori

    Meldola, 47014, Italy

  • Jan Palfijn Hospital

    Merksem, B-2170, Belgium

  • Johanniter Kankenhaus Stendal

    Stendal, 39576, Germany

  • Kantonsspital - St. Gallen

    Sankt Gallen, CH-9007, Switzerland

  • Kantonsspital Aarau

    Aarau, CH-5001, Switzerland

  • Kantonsspital Baden

    Baden, CH-5404, Switzerland

  • Kantonsspital Freiburg

    Fribourg, 1708, Switzerland

  • Kantonsspital Graubuenden

    Chur, CH-7000, Switzerland

  • Kantonsspital Olten

    Olten, CH-4600, Switzerland

  • Kantonsspital Winterthur

    Winterthur, CH-8400, Switzerland

  • Karolinska University Hospital - Huddinge

    Stockholm, S-141 86, Sweden

  • Klinikum Deggendorf

    Deggendorf, 94469, Germany

  • Klinikum Kreuzschwestern Wels GmbH

    Wels, 4600, Austria

  • Klinikum Meiningen GmbH

    Meiningen, 98617, Germany

  • Klinikum Memmingen

    Memmingen, 87700, Germany

  • Klinikum Offenback GmbH

    Offenbach, D-63069, Germany

  • Krankenhaus BHS Linz

    Linz, A-4010, Austria

  • Krankenhaus Lainz

    Vienna, A-1130, Austria

  • Kumamoto University Faculty of Medical and Pharmaceutical Sciences

    Kumamoto, Kumamoto, 860-8556, Japan

  • Kyoto University Hospital

    Kyoto, Kyoto, 606-8507, Japan

  • LKH Villach

    Villach, 9500, Austria

  • Lago Maggiore Oncology Foundation

    Locarno, 6600, Switzerland

  • Landeskrankenhaus Feldkirch

    Feldkirch, A-6807, Austria

  • Lasarettet i Boras

    Borås, 501 15, Sweden

  • Lidkoping Hospital

    Lidköping, S-53185, Sweden

  • M. D. Anderson International Espana SA

    Madrid, 28033, Spain

  • Malarsjukhuset Hospital

    Eskilstuna, Sweden

  • Maroondah Hospital

    Melbourne, Victoria, 3135, Australia

  • Medical University of Vienna

    Vienna, 1090, Austria

  • Medizinische Universitaet Graz

    Graz, A-8036, Austria

  • Misericordia e Dolce Hospital

    Prato, 59100, Italy

  • Naestved Hospital

    Næstved, 4700, Denmark

  • National Institute of Oncology - Budapest

    Budapest, 1122, Hungary

  • Niigata Cancer Center Hospital

    Niigata, Niigata, 951-8566, Japan

  • North West Regional Hospital

    Burnie, Tasmania, 7320, Australia

  • Odense University Hospital

    Odense, DK-5000, Denmark

  • Oncocare Sonnenhof-Klinik Engeriedspital

    Bern, CH-3012, Switzerland

  • Onkologische Schwerpunktpraxis Bielefeld

    Bielefeld, D-33602, Germany

  • Osaka Rosai Hospital

    Sakai, Osaka, 1179-3, Japan

  • Ospedale "la Carita", Locarno

    Locarno, 6600, Switzerland

  • Ospedale Beata Vergine

    Mendrisio, CH-6850, Switzerland

  • Ospedale Civico

    Lugano, CH-6903, Switzerland

  • Ospedale Civile Rimini

    Rimini, 47900, Italy

  • Ospedale degli Infermi - ASL 12

    Biella, 13900, Italy

  • Ospedale di Circolo e Fondazione Macchi

    Varese, 21100, Italy

  • Peter MacCallum Cancer Centre

    East Melbourne, Victoria, 3002, Australia

  • Port Mcquarie Base Hospital

    Port Macquarie, New South Wales, 2444, Australia

  • Praxis Dr. Wilke - Onkologie am Klinikum Fuerth

    Fürth, 90766, Germany

  • Prince of Wales Private Hospital

    Randwick, New South Wales, 2031, Australia

  • Regionalspital

    Thun, 3600, Switzerland

  • Roskilde Amtssygehuset

    Roskilde, 4000, Denmark

  • Royal Hobart Hospital

    Hobart, Tasmania, 7000, Australia

  • Royal Perth Hospital

    Perth, Western Australia, 6000, Australia

  • Russian Academy of Medical Sciences Cancer Research Center

    Moscow, 115478, Russia

  • SRH Zentralklinikum Suhl GmbH

    Suhl, 98527, Germany

  • Sagara Hospital

    Kagoshima, Kagoshima-ken, Japan

  • Sahlgrenska University Hospital

    Gothenburg, S-413 45, Sweden

  • Sandton Oncology Medical Research

    Sandton, 2199, South Africa

  • Sint-Elisabethziekenhuis

    Turnhout, 2300, Belgium

  • Skaraborgs Hospital

    Skövde, 541 85, Sweden

  • Sonderborg Sygehus

    Sønderborg, 6400, Denmark

  • Southern Highlands Cancer Center

    Bowral, New South Wales, 2576, Australia

  • Spedali Civili di Brescia

    Brescia, 25123, Italy

  • St. Johanns-Spital

    Salzburg, A-5020, Austria

  • Szeged University

    Szeged, H-6720, Hungary

  • Tamworth Base Hospital

    Tamworth, New South Wales, 2340, Australia

  • Tata Memorial Hospital

    Mumbai, 400012, India

  • Tokyo Metropolitan - Komagome Hospital

    Tokyo, Tokyo, 113-8677, Japan

  • Tumor Zentrum ZeTup St. Gallen und Chur

    Sankt Gallen, CH-9006, Switzerland

  • Tweed Heads Hospital

    Tweed Heads, New South Wales, 2485, Australia

  • Tygerberg Hospital

    Cape Town, 7505, South Africa

  • U.Z. Gasthuisberg

    Leuven, B-3000, Belgium

  • UniversitaetsSpital Zuerich

    Zurich, CH-8091, Switzerland

  • Universitaetsklinikum Tuebingen

    Tübingen, D-72076, Germany

  • Universitair Ziekenhuis Gent

    Ghent, B-9000, Belgium

  • Vall d'Hebron University Hospital

    Barcelona, 08035, Spain

  • Vejle Sygehus

    Vejle, DK-7100, Denmark

  • Viborg Sygehus

    Viborg, 8800, Denmark

  • Vinzenzkrankenhaus Hannover gGmbH

    Hanover, 30559, Germany

  • Virga Jesse Hospital

    Hasselt, 3500, Belgium

  • Waikato Hospital

    Hamilton, 2020, New Zealand

  • Yao Municipal Hospital

    Osaka, Osaka, 581-0069, Japan

  • Ziekenhuis Netwerk Antwerpen Middelheim

    Antwerp, B-2020, Belgium

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