Condition category
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Contact information



Primary contact

Ms Joan Houghton


Contact details

ATAC secretariat
c/o Charles Bell House
67-73 Riding House Street
United Kingdom
+44 20 3108 7288

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

A randomised double-blind trial comparing arimidex alone with nolvadex alone with arimidex and nolvadex in combination, as adjuvant treatment in post-menopausal women with breast cancer


ATAC (Arimidex, Tamoxifen, Alone or in Combination)

Study hypothesis

Not provided at time of registration

Ethics approval

Not provided at time of registration

Study design

Randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting

Not specified

Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Breast cancer


1. Group A: Arimidex (anstrozole) 1 mg plus Nolvadex (tamoxifen) placebo both daily for 5 years or until recurrence
2. Group B: Arimidex 1 mg plus Nolvadex 20 mg, both daily for 5 years or until recurrence
3. Group C: Arimidex placebo plus Nolvadex 20 mg, both daily for 5 years or until recurrence

Intervention type



Not Specified

Drug names

Primary outcome measure

Not provided at time of registration

Secondary outcome measures

Not provided at time of registration

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Histologically proven operable breast cancer
2. Patients must have completed primary surgery and chemotherapy (if given), and are candidates to receive hormonal adjuvant therapy
3. Deemed to be post-menopausal according to one of the following:
3.1. Aged >60 years
3.2. Bilateral oophorectomy
3.3. Aged <60 years with a uterus and amenorrhoea for at least 12 months
3.4. Aged <60 without a uterus and with follicle stimulating hormone (FSH) >20IU/L
4. No evidence of metastatic disease
5. If chemotherapy was started more than 8 weeks after primary surgery or chemotherapy was completed more than 8 weeks before randomisation the patients is excluded
6. No neo-adjuvant chemotherapy
7. Surgery must have been completed within 8 weeks prior to randomisation
8. No previous hormonal therapy as adjuvant treatment for breast cancer unless:
8.1. Tamoxifen received prior to first surgical procedure for 28 days or less
8.2. Hormonal therapy received pre-surgery in the context of a formal trial
9. Patients who have received tamoxifen as part of any breast cancer prevention trial are to be excluded
10. No previous malignancy within the last 10 years, except squamous or basal cell carcinoma of the skin or carcinoma in situ of the cervix, adequately cone biopsied
11. No treatment with a non-approved drug during the 3 months before randomisation
12. No medical contraindications to any of the treatments in the trial

Participant type


Age group




Target number of participants

Not provided at time of registration

Participant exclusion criteria

Does not match inclusion criteria

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

ATAC secretariat
United Kingdom

Sponsor information


AstraZeneca Clinical Research Group (UK)

Sponsor details

10 Logie Mill
Beaverbank Office Park
Lovie Green Road
United Kingdom

Sponsor type




Funder type


Funder name

AstraZeneca Pharmaceuticals (UK)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

1. 2005 results in
2. 2007 results of long-term safety analysis in
3. 2008 results of 100-month analysis in
4. 2008 five year results in
5. 2010 results on the effect of body mass index on recurrence rates in
6. 2010 results on 10 year analysis of trial in
7. 2010 results in
8. 2012 results in

Publication citations

  1. Results

    Lundgren K, Brown M, Pineda S, Cuzick J, Salter J, Zabaglo L, Howell A, Dowsett M, Landberg G, , Effects of cyclin D1 gene amplification and protein expression on time to recurrence in postmenopausal breast cancer patients treated with anastrozole or tamoxifen: a TransATAC study., Breast Cancer Res., 2012, 14, 2, R57, doi: 10.1186/bcr3161.

  2. Howell A, Cuzick J, Baum M, Buzdar A, Dowsett M, Forbes JF, Hoctin-Boes G, Houghton J, Locker GY, Tobias JS, , Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer., Lancet, 365, 9453, 60-62, doi: 10.1016/S0140-6736(04)17666-6.

  3. , Buzdar A, Howell A, Cuzick J, Wale C, Distler W, Hoctin-Boes G, Houghton J, Locker GY, Nabholtz JM, Comprehensive side-effect profile of anastrozole and tamoxifen as adjuvant treatment for early-stage breast cancer: long-term safety analysis of the ATAC trial., Lancet Oncol., 2006, 7, 8, 633-643, doi: 10.1016/S1470-2045(06)70767-7.

  4. , Forbes JF, Cuzick J, Buzdar A, Howell A, Tobias JS, Baum M, Effect of anastrozole and tamoxifen as adjuvant treatment for early-stage breast cancer: 100-month analysis of the ATAC trial., Lancet Oncol., 2008, 9, 1, 45-53, doi: 10.1016/S1470-2045(07)70385-6.

  5. Eastell R, Adams JE, Coleman RE, Howell A, Hannon RA, Cuzick J, Mackey JR, Beckmann MW, Clack G, Effect of anastrozole on bone mineral density: 5-year results from the anastrozole, tamoxifen, alone or in combination trial 18233230., J. Clin. Oncol., 2008, 26, 7, 1051-1057, doi: 10.1200/JCO.2007.11.0726.

  6. Sestak I, Distler W, Forbes JF, Dowsett M, Howell A, Cuzick J, Effect of body mass index on recurrences in tamoxifen and anastrozole treated women: an exploratory analysis from the ATAC trial., J. Clin. Oncol., 2010, 28, 21, 3411-3415, doi: 10.1200/JCO.2009.27.2021.

  7. Bosse AW, Douglas JF, Berry BC, Jones RL, Karim A, Block-copolymer ordering with a spatiotemporally heterogeneous mobility., Phys. Rev. Lett., 2007, 99, 21, 216101.

Additional files

Editorial Notes